envsetup: mka and reposync functions

    Add specific functions (mka, reposync)

Change-Id: If28a5a206b8bb9ead5242c60f6c1e6af27141b57
reposync: only print updated repos during sync

repo sync redirects updated repositories information to the error
stream, so we can send stdout to /dev/null and the terminal will only
display updated repositories.

Change-Id: I00b15ac18519c9c1efbdeecdae2bcc9b167cf3f4

Conflicts:

	envsetup.sh