Renamed PJ_SVN_REV commandline define to PJ_SVN_REVISION

darcs-hash:20090112160504-58103-07c05274446af7b22080f3a09889f742f1a00d5c
Switched order of precedence between environment and commandline variables of PJSIP SVN repository and revision

darcs-hash:20090112161801-58103-dee7793b0c714b7a886f176dd0be7e266e49f1f7