Looks for problems in proguard config files

Using -keepclasseswithmembernames in a proguard config file is not correct; it can cause some symbols to be renamed which should not be.
Earlier versions of ADT used to create proguard.cfg files with the wrong format. Instead of -keepclasseswithmembernames use -keepclasseswithmembers, since the old flags also implies "allow shrinking" which means symbols only referred to from XML and not Java (such as possibly CustomViews) can get deleted.