Fix compilation with FreeRdp 1.1 and master v2

The API to use remoteFx encoding has changed between master and stable 1.1
branch. This patch should fix compilation for both.
This new version adds checks for the freerdp/version.h file
diff --git a/configure.ac b/configure.ac
index 571bf60..d66dbec 100644
--- a/configure.ac
+++ b/configure.ac
@@ -204,6 +204,11 @@
 if test x$enable_rdp_compositor = xyes; then
   AC_DEFINE([BUILD_RDP_COMPOSITOR], [1], [Build the RDP compositor])
   PKG_CHECK_MODULES(RDP_COMPOSITOR, [freerdp >= 1.1.0])
+
+  SAVED_CPPFLAGS="$CPPFLAGS"
+  CPPFLAGS="$CPPFLAGS $RDP_COMPOSITOR_CFLAGS"
+  AC_CHECK_HEADERS([freerdp/version.h])
+  CPPFLAGS="$SAVED_CPPFLAGS"
 fi
 
 AC_ARG_WITH(cairo,