envsetup: include bash completion script from vendor/cm

Change-Id: Id90d84748df41d6626dfd46befabe0054c6d14e7
Allow disabling DroidDoc build.

Change-Id: Ia842827a46b107bcef0d176deb0ab651e04bfa04
Merge branch 'jellybean' of git://github.com/ParanoidAndroid/android_build into jellybean