winsys/gdi: Custom acquisition of hDC

In d3d10umd it is required to pass D3DKMT_PRESENT in
context_private of flush_frontbuffer, but wgl passes HDC in it.
To accomidate this when gdi_sw_winsys is created functions that
acquire and release hdc from context_private are passed.

Reviewed-by: Jesse Natalie <jenatali@microsoft.com>
Reviewed-by: Feng Jiang <jiangfeng@kylinos.cn>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/27333>

include/meson.build

@@ -20,6 +20,7 @@
 
 inc_include = [include_directories('.')]
 inc_d3d9 = include_directories('D3D9')
+inc_winddk = include_directories('winddk')
 
 # Most things assume that Android headers are in the default include
 # path when compiling for Android so add the stub headers to