* cmake: a couple of msvc compile fixes
Throw error when using multi-config generators.
Add USE_MSVC_STATIC_CRT option for statically linking with CRT.
Set curl's CURL_STATIC_CRT aligned with USE_MSVC_STATIC_CRT.
Fix cmake configs of 7z and OpenAL in msvc build.
Remove unecessary hard coded compiling and linking flags.
Use debug option in windeployqt when configuring for a debug build.
Search for windeployqt tool in configure time.
Add vcpkg's Qt support.
* Fix some typos
Moves GL, minidx12, OpenAL, stblib to 3rdparty
Fixes AppVeyor and CMakeLists (travis-ci.yml doesn't need any changes)
Points directories in the VS solution files to the new ones on the
externals directory
Includes stuff with the < > syntax instead of " "
