bpo-35214: Add _Py_ prefix to MEMORY_SANITIZER def. (GH-10503)


Rename our new MEMORY_SANITIZER define to _Py_MEMORY_SANITIZER.
Project based C Preprocessor namespacing at its finest. :P
(cherry picked from commit 3015fb8ce4d25603434b9b44bb7effb98a481532)

Co-authored-by: Gregory P. Smith <greg@krypto.org>
diff --git a/Python/bootstrap_hash.c b/Python/bootstrap_hash.c
index 76becae..e2afba2 100644
--- a/Python/bootstrap_hash.c
+++ b/Python/bootstrap_hash.c
@@ -20,7 +20,7 @@
 #  endif
 #endif
 
-#ifdef MEMORY_SANITIZER
+#ifdef _Py_MEMORY_SANITIZER
 #  include <sanitizer/msan_interface.h>
 #endif
 
@@ -147,7 +147,7 @@
         else {
             n = syscall(SYS_getrandom, dest, n, flags);
         }
-#  ifdef MEMORY_SANITIZER
+#  ifdef _Py_MEMORY_SANITIZER
         if (n > 0) {
              __msan_unpoison(dest, n);
         }
diff --git a/Python/pymath.c b/Python/pymath.c
index c1606bd..24b8042 100644
--- a/Python/pymath.c
+++ b/Python/pymath.c
@@ -17,7 +17,7 @@
 
 /* inline assembly for getting and setting the 387 FPU control word on
    gcc/x86 */
-#ifdef MEMORY_SANITIZER
+#ifdef _Py_MEMORY_SANITIZER
 __attribute__((no_sanitize_memory))
 #endif
 unsigned short _Py_get_387controlword(void) {