log1p tests: More tests. * tests/test-log1p.h: New file. * modules/log1p-tests (Files): Add tests/test-log1p.h, tests/randomd.c. (Makefile.am): Add randomd.c to test_log1p_SOURCES. * tests/test-log1p.c: Include <float.h> and test-log1p.h. (main): Invoke test_function.