Make .travis.yml and .appveyor.yml work, rename appveyor.yml

The appveyor script can not use a single quoted double quotes string,
like '"C:\Spaces are trouble\"', hence the solution of defining an
environment variable.

appveyor.yml has been renamed to .appveyor.yml to keep consistent with
.travis.yml and to be default hidden.

.appveyor.yml

@@ -7,6 +7,7 @@ environment:
     JOM_LOC: '"C:\Qt\Tools\QtCreator\bin\jom.exe"'
     NSIS_LOC: '"C:\Program Files (x86)\NSIS\"'
     ZIP_LOC: 7z
+    CLANG_FORMAT_LOC: '"C:\Program Files\LLVM\bin\clang-format.exe"'
     COMPILER: msvc
     VSVER: 14
     
@@ -15,9 +16,9 @@ clone_depth: 1
 
 init:
   - set TAG_NAME=%APPVEYOR_REPO_TAG_NAME%
-  - python build_scripts\run-clang-format.py ./src -r --clang-format-executable '"C:\Program Files\LLVM\bin\clang-format.exe"' --color always
 
 build_script:
+  - python ./build_scripts/run-clang-format.py ./src -r --clang-format-executable %CLANG_FORMAT_LOC%  --color always
   - call "build_windows.cmd"
 
 artifacts:

.travis.yml

@@ -10,7 +10,7 @@ install:
   - sudo apt-get install build-essential qtbase5-dev qttools5-dev qtdeclarative5-dev qtmultimedia5-dev qt5-default qttools5-dev-tools
 
 script:
-  - python build_scripts\run-clang-format.py ./src -r --color always
+  - python ./build_scripts/run-clang-format.py ./src -r --color always
   - mkdir build && cd build
   - qmake ..
   - make