contrib: mfx: fix linking with x86 DLL on UWP

intel_gfx_api-x86.dll exports InitialiseMediaSession and DisposeMediaSession, but libqsv_plugin.dll imports InitialiseMediaSession@12 and DisposeMediaSession@4. The name decorations are caused by the APIENTRY modifier, resulting in libqsv_plugin.dll not being able to load intel_gfx_api-x86.dll. It fails with an Entry Point Not Found error. On debug mode UWP, this will crash the CoreCLR.

Should fix LibVLCSharp#374 (closed).

Backport from upstream mfx_dispatch, fixed since https://github.com/lu-zero/mfx_dispatch/commit/7e4d221c36c630c1250b23a5dfa15657bc04c10c.

(cherry picked from commit 18a72511)

Signed-off-by: Steve Lhomme robux4@ycbcr.xyz

Closes #30 (closed)