Make AssertPointerAlignment available to frontend code

We don't need separate definitions for frontend and backend, since the
contained Assert() will take care of the difference.  So this also
makes it simpler overall.

Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Reviewed-by: Michael Paquier <michael@paquier.xyz>
Discussion: https://www.postgresql.org/message-id/f64365b1-d5f9-ef83-41fe-404810f10e5a@enterprisedb.com

src/include/c.h

@@ -793,14 +793,12 @@ typedef NameData *Name;
 
 #define Assert(condition)	((void)true)
 #define AssertMacro(condition)	((void)true)
-#define AssertPointerAlignment(ptr, bndr)	((void)true)
 
 #elif defined(FRONTEND)
 
 #include <assert.h>
 #define Assert(p) assert(p)
 #define AssertMacro(p)	((void) assert(p))
-#define AssertPointerAlignment(ptr, bndr)	((void)true)
 
 #else							/* USE_ASSERT_CHECKING && !FRONTEND */
 
@@ -824,14 +822,14 @@ typedef NameData *Name;
 	((void) ((condition) || \
 			 (ExceptionalCondition(#condition, __FILE__, __LINE__), 0)))
 
+#endif							/* USE_ASSERT_CHECKING && !FRONTEND */
+
 /*
  * Check that `ptr' is `bndr' aligned.
  */
 #define AssertPointerAlignment(ptr, bndr) \
 	Assert(TYPEALIGN(bndr, (uintptr_t)(ptr)) == (uintptr_t)(ptr))
 
-#endif							/* USE_ASSERT_CHECKING && !FRONTEND */
-
 /*
  * ExceptionalCondition is compiled into the backend whether or not
  * USE_ASSERT_CHECKING is defined, so as to support use of extensions