migrate fully to meson build system

- 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.

.gitignore

@@ -9,8 +9,4 @@ core
 .gdb_history
 .gdbinit
 
-.depend
-*.a
-*.o
-*.So
-lib*.so
+build