Increased key repeat rate for non-character input key repeat.

Dodgy - we should have a match here for character input and
non-character input (e.g. holding 'a' vs holding 'backspace' should be
same rate), but for the earlier we don't have the info?

imgui.cpp

@@ -670,7 +670,7 @@ ImGuiIO::ImGuiIO()
     MouseDoubleClickMaxDist = 6.0f;
     MouseDragThreshold = 6.0f;
     KeyRepeatDelay = 0.250f;
-    KeyRepeatRate = 0.020f;
+    KeyRepeatRate = 0.050f;
     UserData = NULL;
 
     // User functions