gplugin/gplugin

Add version macros and tag all existing api with GPLUGIN_AVAILABLE_IN_ALL

Testing Done:
Compiled, ran the unit tests, and gplugin-query.

Reviewed at https://reviews.imfreedom.org/r/1352/
REVIEWBOARD_URL = "https://reviews.imfreedom.org/"
REPOSITORY = "gplugin/gplugin"
REPOSITORY_TYPE = "mercurial"
BRANCH = "default"
LAND_DEST_BRANCH = "default"
LAND_PUSH = False