build: move include to virgl subdir

src/Makefile.am

@@ -45,7 +45,7 @@ libvirglrenderer_ladir = $(libdir)
 libvirglrenderer_la_LIBADD = libvrend.la gallium/auxiliary/libgallium.la
 libvirglrenderer_la_LDFLAGS = $(GM_LDFLAGS) $(EPOXY_LDFLAGS)
 
-libvirglrendererincludedir = ${includedir}
+libvirglrendererincludedir = ${includedir}/virgl
 libvirglrendererinclude_HEADERS = virglrenderer.h virgl_helper.h virgl_egl.h
 
 EXTRA_DIST = gallium/include

virglrenderer.pc.in

@@ -6,5 +6,5 @@ includedir=@includedir@
 Name: virglrenderer
 Description: virgl GL renderer
 Version: @PACKAGE_VERSION@
-Cflags: -I${includedir}
+Cflags: -I${includedir} -I${includedir}/virgl
 Libs: -L${libdir} -lvirglrenderer