build: don't let libtool insert rpath into binaries
build: Find the proper xcb/pcre dependencies
build: add WIP dependency builder.

This is in constant flux and is not ready for any real use.
travis: initial config
gitian: replace descriptors
Use of INCLUDES deprecated, renamed to DEPS_INCLUDES.
Travis CI Indicator Image, Hook Link.
Tidy away pkg.m4 into dir with other m4 scripts.