tests: Minor adjustments selecting which tests are run on each platform.
The intent is for 'make test' to pass cleanly on each platform, and thus easier
spotting of regressions. Linux is best supported by most tests running and
passing. Mac OSX passes mosts tests that do not make/link with binary files,
due to lack of mach-o file support.
!!! I have very limited knowledge of Windows platform, and cannot comment why
all tests(1) fail. I have posted to newsgroup asking for someone to test
Windows platform.