Update PR for SANITIZER_MMAP_BEGIN

Author: jakeegan

compiler-rt/lib/sanitizer_common/sanitizer_platform.h

@@ -319,7 +319,11 @@
 #endif
 
 // The first address that can be returned by mmap.
-#define SANITIZER_MMAP_BEGIN 0
+#if SANITIZER_AIX && SANITIZER_WORDSIZE == 64
+# define SANITIZER_MMAP_BEGIN 0x0a00000000000000ULL
+#else
+# define SANITIZER_MMAP_BEGIN 0
+#endif
 
 // The range of addresses which can be returned my mmap.
 // FIXME: this value should be different on different platforms.  Larger values