unconditionally define reallocarray

deal with systems missing it but with it exported as a symbol

include/compat/stdlib.h

@@ -33,9 +33,7 @@ void freezero(void *ptr, size_t sz);
 const char * getprogname(void);
 #endif
 
-#ifndef HAVE_REALLOCARRAY
 void *reallocarray(void *, size_t, size_t);
-#endif
 
 #ifndef HAVE_RECALLOCARRAY
 void *recallocarray(void *, size_t, size_t, size_t);