Export missing vgcontext*.h headers and remove libvgi.mmp due to collision with KhronosRI.
[QueryString_Extensions_tb92]
CountExtensionsEGL=2
ExtensionEGL0=EGL_NOK__private__signal_sync
ExtensionEGL1=EGL_KHR_reusable_sync
CountExtensionsVG=0
[QueryString_Extensions]
CountExtensionsEGL=2
ExtensionEGL0=EGL_NOK__private__signal_sync
ExtensionEGL1=EGL_KHR_reusable_sync
CountExtensionsVG=0