prepare for Mac OS 10.10 (Yosemite)

One thing to notice is the setting of the environment variable
MACOSX_DEPLOYMENT_TARGET, described in M2/INSTALL.
prepare for Mac OS 10.10 (Yosemite), part 2
fix makefiles so the submodules don't get recompiled so often
get --enable-strip option to work, and

fix makefiles to accommodate not using pkg-config with mathic and mathicgb
strip more binaries

and check, afterwards, that they did all get stripped
fix check-stripped test
update INSTALL
update INSTALL
update INSTALL
Merge branch 'release-1.7' of github.com:Macaulay2/M2 into release-1.7
Merge branch 'release-1.7'
fix makefiles