ci: add ccache support

ci: add ccache support

this enables and implements full support for ccache on travis builds

fix T7126

Differential Revision: https://phab.enlightenment.org/D6605

=also includes previously-submitted patches=

ci: split out ccache config setup into separate script

this provides a more unified place to set ccache options

also enable ccache compression to cut down on cache upload/download overhead

ref D6613

ci: zero ccache stats before build and add some comments for options used

zeroing the stats before each build will provide more insight into the cache
performance for each build

ref D6621

ci: break out ccache stat printing into separate script

continue to make travis.yml more readable

ref D6622

ci: add more ccache config options to improve cache direct hits

ci: disable second cpp run for ccache

this should avoid running cpp twice for files

https://ccache.samba.org/manual.html#_the_preprocessor_mode