Update wcsmbs tests to use the support test driver
Replaced test-skeleton.c with support/test-driver.c and
adjusted the tests accordinly.
Checked on x86_64-linux-gnu.
* wcsmbs/tst-btowc.c: Import support/test-driver.c and remove
the TEST_FUNCTION macro definition.
* wcsmbs/tst-mbrtowc2.c: Likewise.
* wcsmbs/tst-mbsrtowcs.c: Likewise.
* wcsmbs/tst-wchar-h.c: Likewise.
* wcsmbs/tst-wcpncpy.c: Likewise.
* wcsmbs/tst-wcrtomb.c: Likewise.
* wcsmbs/tst-wcsnlen.c: Likewise.
* wcsmbs/tst-wcstof.c: Likewise.