version.h: Add version check macro

Make it easier to check for a Weston version.

src/version.h.in

@@ -28,4 +28,10 @@
 #define WESTON_VERSION_MICRO @WESTON_VERSION_MICRO@
 #define WESTON_VERSION "@WESTON_VERSION@"
 
+/* Can be used like #if WESTON_VERSION_AT_LEAST(1, 2, 0) */
+#define WESTON_VERSION_AT_LEAST(major, minor, micro) \
+        (WESTON_VERSION_MAJOR == (major) && \
+         WESTON_VERSION_MINOR == (minor) && \
+         WESTON_VERSION_MICRO >= (micro))
+
 #endif