Remove ancient implicit make rules

GNU Make contains some (ancient) implicit rules, that try to
_automatically_ extract source files from RCS/SCCS version control
systems. This is unneeded, and it pollutes the make -d output
significantly: after removing these rules (by defining empty targets
for their patterns), make -d line count goes from 5.3K to 3.3K.

Signed-off-by: Iustin Pop <iustin@google.com>
Reviewed-by: Guido Trotter <ultrotter@google.com>