Changes windows build and PNG cmake to reflect latests libpng builds

autobuild.xml

@@ -1004,9 +1004,9 @@
             <key>archive</key>
             <map>
               <key>hash</key>
-              <string>dd0e68bde099def37c6a7527673aa672</string>
+              <string>735a955e6442733e2342ab12c1087488</string>
               <key>url</key>
-              <string>http://s3.amazonaws.com/viewer-source-downloads/install_pkgs/libpng-1.2.35-windows-20101001a.tar.bz2</string>
+              <string>http://automated-builds-secondlife-com.s3.amazonaws.com/hg/repo/3p-libpng/rev/221747/arch/CYGWIN/installer/libpng-1.5.1-windows-20110221.tar.bz2</string>
             </map>
             <key>name</key>
             <string>windows</string>

indra/cmake/PNG.cmake

@@ -8,6 +8,6 @@ if (STANDALONE)
   include(FindPNG)
 else (STANDALONE)
   use_prebuilt_binary(libpng)
-  set(PNG_LIBRARIES png12)
-  set(PNG_INCLUDE_DIRS ${LIBS_PREBUILT_DIR}/include/libpng12)
+  set(PNG_LIBRARIES libpng15)
+  set(PNG_INCLUDE_DIRS ${LIBS_PREBUILT_DIR}/include/libpng15)
 endif (STANDALONE)