Blacklist xlc 32-bit inlining.

Per a suggestion from Tom Lane.  Back-patch to 9.0 (all supported
versions).  While only 9.4 and up have code known to elicit this
compiler bug, we were disabling inlining by accident until commit
43d89a23d5.

config/test_quiet_include.h

@@ -3,3 +3,12 @@
  * of the PGAC_C_INLINE macro in config/c-compiler.m4.
  */
 static inline int fun () { return 0; }
+
+/*
+ * "IBM XL C/C++ for AIX, V12.1" miscompiles, for 32-bit, some inline
+ * expansions of ginCompareItemPointers() "long long" arithmetic.  To take
+ * advantage of inlining, build a 64-bit PostgreSQL.
+ */
+#if defined(__ILP32__) && defined(__IBMC__)
+#error "known inlining bug"
+#endif