tests: omit MEMCHR etc as no longer needed

tests: omit MEMCHR etc as no longer needed

* tests/test-memchr.c (MEMCHR):
* tests/test-memchr2.c (MEMCHR2):
* tests/test-memrchr.c (MEMRCHR):
* tests/test-rawmemchr.c (RAWMEMCHR):
Remove these macros, as the code never adds to their results.
All uses replaced by original functions.

* tests/test-memchr.c (lib_memchr, volatile_memchr, memchr)