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.

test/Makefile

@@ -1,14 +0,0 @@
-all:
-
-install:
-
-ignore:
-
-check test::
-	./runtests.sh
-
-verbose-test:
-	VERBOSE=yes ./runtests.sh
-
-clean:
-	rm -rf *.out tmp-*