log10f tests: More tests. * modules/log10f-tests (Files): Add tests/test-log10.h, tests/minus-zero.h, tests/randomf.c. (Makefile.am): Add randomf.c to test_log10f_SOURCES. * tests/test-log10f.c: Include <float.h>, minus-zero.h, test-log10.h. (main): Invoke test_function.