gui: Make framerate configurable

Default framerate is 30 FPS

Change-Id: Ia05357663905a3babecb95b1e3531ae45fc854c5
(cherry picked from commit 5d3e488568445b830f11aed39bf9542a8be501bf)
diff --git a/gui/libguitwrp_defaults.go b/gui/libguitwrp_defaults.go
index 9d7dcef..472836e 100644
--- a/gui/libguitwrp_defaults.go
+++ b/gui/libguitwrp_defaults.go
@@ -323,6 +323,10 @@
 		cflags = append(cflags, "-DTW_H_OFFSET="+getMakeVars(ctx, "TW_H_OFFSET"))
 	}
 
+        if getMakeVars(ctx, "TW_FRAMERATE") != "" {
+                cflags = append(cflags, "-DTW_FRAMERATE="+getMakeVars(ctx, "TW_FRAMERATE"))
+        }
+
 	if getMakeVars(ctx, "TW_ROUND_SCREEN") == "true" {
 		cflags = append(cflags, "-DTW_ROUND_SCREEN")
 	}