bump version to 0.12.6-rc

Also remove custom-qt4-mxe-win which is redundant and would
take too long after the recent packaging changes.

.travis.yml

@@ -30,9 +30,6 @@ matrix:
       osx_image:  xcode9.3
       env:        TARGET=custom-qt4-macos
 
-    - os:         linux
-      env:        TARGET=custom-qt4-mxe-win
-
     - os:         windows
       env:        TARGET=custom-qt4-windows
 
@@ -47,7 +44,6 @@ script:
     if   [[ $TARGET == "system-qt4-linux"   ]]; then qmake-qt4 CONFIG+=silent && make;
     elif [[ $TARGET == "system-qt5-linux"   ]]; then /usr/lib/x86_64-linux-gnu/qt5/bin/qmake CONFIG+=silent && make;
     elif [[ $TARGET == "custom-qt4-linux"   ]]; then ../packaging/build compile-docker stretch-amd64   $PWD ../build;
-    elif [[ $TARGET == "custom-qt4-mxe-win" ]]; then ../packaging/build compile-docker mxe-cross-win64 $PWD ../build;
     elif [[ $TARGET == "custom-qt4-windows" ]]; then
         choco install -yr --no-progress python2 nsis vcbuildtools && \
         choco install -yr --no-progress cmake --installargs 'ADD_CMAKE_TO_PATH=System' && \

VERSION

@@ -1 +1 @@
-0.12.6-dev
+0.12.6-rc