- drop old build system
- move shared include and source files to common directory
- drop "rc-" prefix from shared include and source files
- move executable-specific code to individual directories under src
- adjust top-level .gitignore file for new build system
This closes#489.
The libeinfo library has no consumers other than OpenRC, so there is no
reason for it to be maintained as a library. The einfo routines are now
an object that links with the rc binary.