Remove epicscorelibs.path dependency on compiler

[coretl]

Before this commit, an import of epicscorelibs.path would compute some variables, including about the compiler, to determine the OS_CLASS. However this was unused except in tests. This commit removes epicscorelibs.path.OS_CLASS and replaces references to it with platform.system() instead.

Fixes #42, fixes #41

[AlexanderWells-diamond]

This appears to not work as expected as it does not suppress the logging messages; I still see the messages appear when following the instructions in this comment.

This is after a pip install -e . of this branch checkout.

[coretl]

This appears to not work as expected as it does not suppress the logging messages; I still see the messages appear when following the instructions in this comment.

This is after a pip install -e . of this branch checkout.

The instructions provoke it by doing a direct import of epicscorelibs.config. However in production it is provoked by doing an import of epicscorelibs.path.pyepics, which no longer does an import of epicscorelibs.config internally...

[AlexanderWells-diamond]

Ah understood, my reproduce wasn't accurate to the actual production issue. As I think further changes are incoming based on discussion in the issue, I'll hold off further review at the moment.

[AlexanderWells-diamond]

I think these changes are good, but I would like to see the commit message and PR title / description updated to better reflect what was done.

I'm also not sure why the version number appears to be marked as a change; the master version of setup.py definitely already has the version with a2 on the end...

[AlexanderWells-diamond]

All looks good now