Overhauled llvm/clang docs builds. Closes PR6613.

NOTE: 2nd part changeset for cfe trunk to follow.

*** PRE-PATCH ISSUES ADDRESSED

- clang api docs fail build from objdir
- clang/llvm api docs collide in install PREFIX/
- clang/llvm main docs collide in install
- clang/llvm main docs have full of hard coded destination
  assumptions and make use of absolute root in static html files;
  namely CommandGuide tools hard codes a website destination
  for cross references and some html cross references assume
  website root paths

*** IMPROVEMENTS

- bumped Doxygen from 1.4.x -> 1.6.3
- splits llvm/clang docs into 'main' and 'api' (doxygen) build trees
- provide consistent, reliable doc builds for both main+api docs
- support buid vs. install vs. website intentions
- support objdir builds
- document targets with 'make help'
- correct clean and uninstall operations
- use recursive dir delete only where absolutely necessary
- added call function fn.RMRF which safeguards against botched 'rm -rf';
  if any target (or any variable is evaluated) which attempts
  to remove any dirs which match a hard-coded 'safelist', a verbose
  error will be printed and make will error-stop.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@103213 91177308-0d34-0410-b5e6-96231b3b80d8

configure

@@ -736,11 +736,13 @@ INSTALL_PROGRAM
 INSTALL_SCRIPT
 INSTALL_DATA
 BZIP2
+CAT
 DOXYGEN
 GROFF
 GZIP
 POD2HTML
 POD2MAN
+PDFROFF
 RUNTEST
 TCLSH
 ZIP
@@ -8016,6 +8018,46 @@ echo "${ECHO_T}no" >&6; }
 fi
 
 
+# Extract the first word of "cat", so it can be a program name with args.
+set dummy cat; ac_word=$2
+{ echo "$as_me:$LINENO: checking for $ac_word" >&5
+echo $ECHO_N "checking for $ac_word... $ECHO_C" >&6; }
+if test "${ac_cv_path_CAT+set}" = set; then
+  echo $ECHO_N "(cached) $ECHO_C" >&6
+else
+  case $CAT in
+  [\\/]* | ?:[\\/]*)
+  ac_cv_path_CAT="$CAT" # Let the user override the test with a path.
+  ;;
+  *)
+  as_save_IFS=$IFS; IFS=$PATH_SEPARATOR
+for as_dir in $PATH
+do
+  IFS=$as_save_IFS
+  test -z "$as_dir" && as_dir=.
+  for ac_exec_ext in '' $ac_executable_extensions; do
+  if { test -f "$as_dir/$ac_word$ac_exec_ext" && $as_executable_p "$as_dir/$ac_word$ac_exec_ext"; }; then
+    ac_cv_path_CAT="$as_dir/$ac_word$ac_exec_ext"
+    echo "$as_me:$LINENO: found $as_dir/$ac_word$ac_exec_ext" >&5
+    break 2
+  fi
+done
+done
+IFS=$as_save_IFS
+
+  ;;
+esac
+fi
+CAT=$ac_cv_path_CAT
+if test -n "$CAT"; then
+  { echo "$as_me:$LINENO: result: $CAT" >&5
+echo "${ECHO_T}$CAT" >&6; }
+else
+  { echo "$as_me:$LINENO: result: no" >&5
+echo "${ECHO_T}no" >&6; }
+fi
+
+
 # Extract the first word of "doxygen", so it can be a program name with args.
 set dummy doxygen; ac_word=$2
 { echo "$as_me:$LINENO: checking for $ac_word" >&5
@@ -8216,6 +8258,46 @@ echo "${ECHO_T}no" >&6; }
 fi
 
 
+# Extract the first word of "pdfroff", so it can be a program name with args.
+set dummy pdfroff; ac_word=$2
+{ echo "$as_me:$LINENO: checking for $ac_word" >&5
+echo $ECHO_N "checking for $ac_word... $ECHO_C" >&6; }
+if test "${ac_cv_path_PDFROFF+set}" = set; then
+  echo $ECHO_N "(cached) $ECHO_C" >&6
+else
+  case $PDFROFF in
+  [\\/]* | ?:[\\/]*)
+  ac_cv_path_PDFROFF="$PDFROFF" # Let the user override the test with a path.
+  ;;
+  *)
+  as_save_IFS=$IFS; IFS=$PATH_SEPARATOR
+for as_dir in $PATH
+do
+  IFS=$as_save_IFS
+  test -z "$as_dir" && as_dir=.
+  for ac_exec_ext in '' $ac_executable_extensions; do
+  if { test -f "$as_dir/$ac_word$ac_exec_ext" && $as_executable_p "$as_dir/$ac_word$ac_exec_ext"; }; then
+    ac_cv_path_PDFROFF="$as_dir/$ac_word$ac_exec_ext"
+    echo "$as_me:$LINENO: found $as_dir/$ac_word$ac_exec_ext" >&5
+    break 2
+  fi
+done
+done
+IFS=$as_save_IFS
+
+  ;;
+esac
+fi
+PDFROFF=$ac_cv_path_PDFROFF
+if test -n "$PDFROFF"; then
+  { echo "$as_me:$LINENO: result: $PDFROFF" >&5
+echo "${ECHO_T}$PDFROFF" >&6; }
+else
+  { echo "$as_me:$LINENO: result: no" >&5
+echo "${ECHO_T}no" >&6; }
+fi
+
+
 # Extract the first word of "runtest", so it can be a program name with args.
 set dummy runtest; ac_word=$2
 { echo "$as_me:$LINENO: checking for $ac_word" >&5
@@ -11275,7 +11357,7 @@ else
   lt_dlunknown=0; lt_dlno_uscore=1; lt_dlneed_uscore=2
   lt_status=$lt_dlunknown
   cat > conftest.$ac_ext <<EOF
-#line 11278 "configure"
+#line 11360 "configure"
 #include "confdefs.h"
 
 #if HAVE_DLFCN_H
@@ -20300,9 +20382,6 @@ ac_config_files="$ac_config_files Makefile.config"
 ac_config_files="$ac_config_files llvm.spec"
 
 
-ac_config_files="$ac_config_files docs/doxygen.cfg"
-
-
 ac_config_files="$ac_config_files tools/llvmc/plugins/Base/Base.td"
 
 
@@ -20922,7 +21001,6 @@ do
     "include/llvm/System/DataTypes.h") CONFIG_HEADERS="$CONFIG_HEADERS include/llvm/System/DataTypes.h" ;;
     "Makefile.config") CONFIG_FILES="$CONFIG_FILES Makefile.config" ;;
     "llvm.spec") CONFIG_FILES="$CONFIG_FILES llvm.spec" ;;
-    "docs/doxygen.cfg") CONFIG_FILES="$CONFIG_FILES docs/doxygen.cfg" ;;
     "tools/llvmc/plugins/Base/Base.td") CONFIG_FILES="$CONFIG_FILES tools/llvmc/plugins/Base/Base.td" ;;
     "tools/llvm-config/llvm-config.in") CONFIG_FILES="$CONFIG_FILES tools/llvm-config/llvm-config.in" ;;
     "setup") CONFIG_COMMANDS="$CONFIG_COMMANDS setup" ;;
@@ -21176,11 +21254,13 @@ INSTALL_PROGRAM!$INSTALL_PROGRAM$ac_delim
 INSTALL_SCRIPT!$INSTALL_SCRIPT$ac_delim
 INSTALL_DATA!$INSTALL_DATA$ac_delim
 BZIP2!$BZIP2$ac_delim
+CAT!$CAT$ac_delim
 DOXYGEN!$DOXYGEN$ac_delim
 GROFF!$GROFF$ac_delim
 GZIP!$GZIP$ac_delim
 POD2HTML!$POD2HTML$ac_delim
 POD2MAN!$POD2MAN$ac_delim
+PDFROFF!$PDFROFF$ac_delim
 RUNTEST!$RUNTEST$ac_delim
 TCLSH!$TCLSH$ac_delim
 ZIP!$ZIP$ac_delim
@@ -21233,7 +21313,7 @@ LIBOBJS!$LIBOBJS$ac_delim
 LTLIBOBJS!$LTLIBOBJS$ac_delim
 _ACEOF
 
-  if test `sed -n "s/.*$ac_delim\$/X/p" conf$$subs.sed | grep -c X` = 92; then
+  if test `sed -n "s/.*$ac_delim\$/X/p" conf$$subs.sed | grep -c X` = 94; then
     break
   elif $ac_last_try; then
     { { echo "$as_me:$LINENO: error: could not make $CONFIG_STATUS" >&5