macosx: build-dmg.sh: add note about new py2app v0.9 warnings
macosx: build-dmg.sh: add warning if not run from a Git repository
macosx: build-dmg.sh: revise initial message; check working directory
macosx: mac-app.py: add option to specify binary architecture set
macosx: build-dmg.sh: use getopts instead of variables
macosx: build-dmg.sh: add option for binary architecture set
macosx: update INSTALL with reference to '-h' option of build-dmg.sh
macosx: update patch files
macosx: build-dmg.sh: suppress normal output of appdmg
macosx: build-dmg.sh: helpful message at end with DMG location
macosx: build-dmg.sh: use variable instead of hardcoded value
macosx: build-dmg.sh: reliably handle architecture problems
Merge pull request #461 from dliessi/mac-arch

Mac packaging: better handling of binary architecture + other improvements