Introduce rebar build system
autotools can still be used
ebin/exmpp.app file is generated from src/exmpp.app.src (the erlang way ?) to get vsn from git when applicable
exmpp_known* headers and sources generated with escripts
Ignore rebar build introduced files
Fix compilation of port drivers
Cleanup rebar.config
Fix generation of exmpp_known_*.{hrl,erl} files from escript
Fix Makefile target for exmpp_known* files
Use makefile to generate headers (for soruce modifications check)
Use Makefile to generate erl source files
Update make-specs-list wrt/ xmpp.org website
Include OCCI and XMLSchema schema to known XML elements
Merge remote-tracking branch 'origin/rebar2'