Makefile.include: add verbosity control (make V=1 for previous behaviour)

This shortens $(CC) and $(AR) lines to a much more readable length,
making warnings stick out clearly.

The spaces after "CC" and "AR" are to reserve space for other operations
that may use longer names, such as the communly found "BUILD" or
"GENERATE".
Merge pull request #305 from frtos-wpan/pull-verbosity

Makefile.include: add verbosity control (make V=1 for old behaviour)