Makefile.rules can now tell the OMK tester that the test cannot be executed.

Makefile.rules can now tell the OMK tester that the test cannot be executed.

If OMK is executed by tester.py, base snippet calls -check targets for
each pass and defines macro 'canttest'. The canttest macro can be used
by the -check targets or at other places. It notifies the tester that
this test cannot be executed because of something is missing for
example.

This way, the check for "canttest" don't have to be in runtest
scripts, which allows to execute more tests and skip only those, which
relly need some unavailable feature.

Tester application was enhanced to produce results not only by
testcase but also by rules. The results also contains links to test
script and directory, so it is easy to see quicky what a given error
mean.

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