Don't intepret .a{commits} as a minor version

When the minor version is missing from the tag, the debian version
looks like 2013.2.a31. This is greater than 2013.2.1.a32 so when the
tag is moved forward after a minor release, the package won't upgrade.

Changed the debian version format to 2013.2.1+a32~gabcdef-1 to handle
this.

Change-Id: If29c4f48a37398616580aa433d1e6bd58942beca
Merge "Don't intepret .a{commits} as a minor version"