envsetup: Really fix PROMPT_COMMAND handling

 * Add ANDROID_NO_PROMPT_COMMAND to not change it at all.
 * Export ANDROID_PROMPT_PREFIX so it can be used elsewhere.

Change-Id: Ib2a487404d3b8a367a21582e8a0ce69c2d212a9a
envsetup: More PROMPT_COMMAND

* Get rid of ANDROID_NO_PROMPT_COMMAND, the pre-existing STAY_OFF_MY_LAWN
does the same thing
* Remove any pre-existing android prefixes to avoid accumulation
scenarios in consecutive builds (i.e., multiple build identification
strings in hardstatus)

Change-Id: I86661e066e18ea6ad0c742fa1dc6555780fa5441
roomservice: Allow following up tag references

This is now needed for release builds

Change-Id: I8c5f87341059b3b15ee853312b71df73790ad0d8
Merge branch 'cm-10.1' of github.com:CyanogenMod/android_build into cm-10.1
Merge branch 'cm-10.1' of github.com:PecanCM/android_build into cm-10.1