Update Xcode project settings.
Set default architectures to the default value instead of the 64-bit default.
Makefile changes:
Don't set CC. (makes scan-build work)
Remove -arch, just build for the default arch instead.
Use -Os instead of -O2.
Remove -g.
Update README.md with the new pwgen help output.
Remove repository link from SFPasswordAssistant.h.