Remove base-* directories from gm expected/actual paths; just use platform names

trunk/tools/tests/rebaseline/input/json1/Test-Mac10.6-MacMini4.1-GeForce320M-x86-Release/expected-results.json

 {
    "expected-results" : {
       "aaclip_565.png" : {
          "allowed-digests" : [
             [ "bitmap-64bitMD5", 12345 ]
          ],
          "ignore-failure" : false
       },
       "aaclip_8888.png" : {
          "allowed-digests" : [
             [ "bitmap-64bitMD5", 67890 ]
          ],
          "ignore-failure" : false
       },
       "aaclip_gpu.png" : {
          "allowed-digests" : [
             [ "bitmap-64bitMD5", 11899819492385205974 ]
          ],
          "ignore-failure" : false
       },
       "aaclip_pdf.png" : {
          "allowed-digests" : null,
          "ignore-failure" : false
       }
    }
 }