Remove obsolete Travis CI support.

.travis.yml

@@ -1,28 +0,0 @@
-language: cpp
-sudo: required
-
-os:
-  - linux
-  - osx
-
-osx_image: xcode11.3
-
-dist: focal
-
-addons:
-  apt:
-    sources:
-    - ubuntu-toolchain-r-test
-    packages:
-    - gcc-7
-    - g++-7
-
-install:
-  - source build/InstallMono.sh
-  - build/InstallNugets.sh  
-  - if [ "$TRAVIS_OS_NAME" = "linux" ] && [ "$CXX" = "g++" ]; then export CXX="g++-7" CC="gcc-7"; fi
-  - if [ "$TRAVIS_OS_NAME" = "linux" ]; then PREMAKE=build/premake5-linux; else PREMAKE=build/premake5-osx; fi
-  - $PREMAKE --file=build/scripts/LLVM.lua download_llvm
-
-script: |
-  build/Compile.sh && build/RunTests.sh