Revert "Eliminate 'different const qualifiers' MSVC warnings in noop1…

…_ptr"

Issue #627 (bdwgc).

This reverts commit f985d63.

Reason: GC_noop1_ptr() should not tell the compiler that the argument
is a const pointer.

include/gc/gc.h

@@ -1530,7 +1530,7 @@ GC_API int GC_CALL GC_invoke_finalizers(void);
 GC_API void GC_CALL GC_noop1(GC_word);
 
 /* Same as GC_noop1() but for a pointer.        */
-GC_API void GC_CALL GC_noop1_ptr(const volatile void *);
+GC_API void GC_CALL GC_noop1_ptr(volatile void *);
 
 /* GC_set_warn_proc can be used to redirect or filter warning messages. */
 /* p may not be a NULL pointer.  msg is printf format string (arg must  */

mark.c

@@ -48,7 +48,7 @@ GC_API void GC_CALL GC_noop1(GC_word x)
 # endif
 }
 
-GC_API void GC_CALL GC_noop1_ptr(const volatile void *p)
+GC_API void GC_CALL GC_noop1_ptr(volatile void *p)
 {
   GC_noop1(ADDR(p));
 }