lib: Implement dependency-based initcall mechanism

Signed-off-by: Andrew Andrianov <andrew@ncrmnt.org>
doc: Update documentation to include INITCALL stuff

Signed-off-by: Andrew Andrianov <andrew@ncrmnt.org>
buildsystem: Implement build-graphing, optimize things

Signed-off-by: Andrew Andrianov <andrew@ncrmnt.org>