Individual autoconf function broken out of acincludes.m4. This change

per the recommended style guide for autoconf and so that individual
autoconf functions can more easily be shared across projects.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@16223 91177308-0d34-0410-b5e6-96231b3b80d8

autoconf/m4/func_mmap_file.m4

@@ -0,0 +1,32 @@
+#
+# Check for the ability to mmap a file.  
+#
+AC_DEFUN([AC_FUNC_MMAP_FILE],
+[AC_CACHE_CHECK(for mmap of files,
+ac_cv_func_mmap_file,
+[AC_LANG_SAVE
+  AC_LANG_C
+  AC_TRY_RUN([
+#ifdef HAVE_SYS_TYPES_H
+#include <sys/types.h>
+#endif
+
+#ifdef HAVE_SYS_MMAN_H
+#include <sys/mman.h>
+#endif
+
+#ifdef HAVE_FCNTL_H
+#include <fcntl.h>
+#endif
+
+  int fd;
+  int main () {
+  fd = creat ("foo",0777); fd = (int) mmap (0, 1, PROT_READ, MAP_SHARED, fd, 0); unlink ("foo"); return (fd != (int) MAP_FAILED);}],
+  ac_cv_func_mmap_file=yes, ac_cv_func_mmap_file=no)
+  AC_LANG_RESTORE
+])
+if test "$ac_cv_func_mmap_file" = yes; then
+   AC_DEFINE([HAVE_MMAP_FILE],[],[Define if mmap() can map files into memory])
+   AC_SUBST(MMAP_FILE,[yes])
+fi
+])