mfvideosrc: Enable WinRT capture impl. for desktop target

... if target OS version was specified as Windows 10.
When enabled, desktop application can select target capture
implementation between WinRT and Win32
via GST_USE_MF_WINRT_CAPTURE environment
(e,g., GST_USE_MF_WINRT_CAPTURE=1 for WinRT impl.).
Default is Win32 implementation in case of desktop target.

Part-of: <!1434>
29 jobs for master in 3 minutes and 21 seconds (queued for 10 seconds)
Status Job ID Name Coverage
  Build Docker
passed #3610279
alpine amd64 manifest builder docker

00:00:21

passed #3610278
android docker

00:00:30

passed #3610277
cerbero fedora amd64 docker

00:00:26

passed #3610276
fedora amd64 docker

00:00:25

passed #3610280
gst-indent amd64 docker

00:02:03

 
  Preparation
passed #3610282
gst indent

00:00:46

manual #3610281
manual
manifest
 
  Build
created #3610291
gstreamer
build cerbero cross-android universal
created #3610295
gst-ios-13.2
build cerbero cross-ios universal
created #3610292
gstreamer
build cerbero cross win32
created #3610293
gstreamer
build cerbero cross win64
created #3610290
gstreamer
build cerbero fedora x86_64
created #3610294
gst-macos-10.15
build cerbero macos x86_64
created #3610286
build clang fedora x86_64
created #3610289
1809 windows docker allowed to fail manual
build msys2
created #3610283
build nodebug fedora x86_64
created #3610284
build static fedora x86_64
created #3610285
build static nodebug fedora x86_64
created #3610287
1809 windows docker
build vs2017 amd64
created #3610288
1809 windows docker
build vs2017 x86
 
  Test
created #3610296
gstreamer
check fedora
created #3610297
gstreamer
integration testsuites fedora 1/4
created #3610298
gstreamer
integration testsuites fedora 2/4
created #3610299
gstreamer
integration testsuites fedora 3/4
created #3610300
gstreamer
integration testsuites fedora 4/4
created #3610301
gstreamer
valgrind bad
 
  Integrate
created #3610302
cross-android universal examples
created #3610304
gst-ios-13.2
cross-ios universal examples
created #3610303
documentation