tests: Make last patch side-effect free.

tests: Make last patch side-effect free.

* tests/test-bsearch.c: Use another volatile function pointer variable.
* tests/test-memccpy.c: Likewise.
* tests/test-memchr.c: Likewise.
* tests/test-memcmp.c: Likewise.
* tests/test-memcpy.c: Likewise.
* tests/test-memmove.c: Likewise.
* tests/test-memset.c: Likewise.
* tests/test-memset_explicit.c: Likewise.
* tests/test-qsort.c: Likewise.
* tests/test-strncat.c: Likewise.
* tests/test-strncmp.c: Likewise.
* tests/test-strncpy.c: Likewise.
* tests/test-strndup.c: Likewise.
* tests/test-wcsncat.c: Likewise.
* tests/test-wcsncmp.c: Likewise.
* tests/test-wcsncpy.c: Likewise.
* tests/test-wmemchr.c: Likewise.
* tests/test-wmemcmp.c: Likewise.
* tests/test-wmemcpy.c: Likewise.
* tests/test-wmemmove.c: Likewise.
* tests/test-wmemset.c: Likewise.