checkstyle: improve speed by checking only recently changed files

checkstyle: improve speed by checking only recently changed files

This change makes checkstyle much faster by checking only recently
changed files. It only checks files changed in last commit and files
which are localy modified. Old behavior is preserved by specifying
argument "--full" when invoking script.

In addition "make checkstyle" and "make "fixstyle" actions are added
to the top-level Makefile.

Change-Id: I7d86225bd282f32ee508e7f52692a3778ac8dcda
Signed-off-by: Damjan Marion <[email protected]>