Isolate machine-dependent use of <alloca.h> in "Support/Alloca.h",

so that we can easily change its use to be conditional on the result of
an autoconf test later.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@6723 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CodeGen/InstrSelection/InstrForest.cpp

@@ -21,7 +21,7 @@
 #include "llvm/Type.h"
 #include "llvm/CodeGen/MachineInstr.h"
 #include "Support/STLExtras.h"
-#include <alloca.h>
+#include "Support/Alloca.h"
 using std::cerr;
 using std::vector;