Add a comment, and fix a bug where AllocateRW recurred to AllocateRWX instead of itself.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@48677 91177308-0d34-0410-b5e6-96231b3b80d8

lib/System/Unix/Memory.inc

@@ -103,7 +103,7 @@ llvm::sys::Memory::AllocateRW(unsigned NumBytes, const MemoryBlock* NearBlock,
                     flags, fd, 0);
   if (pa == MAP_FAILED) {
     if (NearBlock) //Try again without a near hint
-      return AllocateRWX(NumBytes, 0);
+      return AllocateRW(NumBytes, 0);
 
     MakeErrMsg(ErrMsg, "Can't allocate RWX Memory");
     return MemoryBlock();