Removed unnecessary includes and inline definitions.

Dominic's Hamon review request: https://reviews.apache.org/r/18295
mergeable to today's master version, this is a lightened version to
make review easier.  Note I see an improvements of ~7.5% of the
compile time.

Review: https://reviews.apache.org/r/23745
More docs for attributes and resources.

Review: https://reviews.apache.org/r/23752
Removed trailing '/' in Makefile.am.

Review: https://reviews.apache.org/r/23829