GUACAMOLE-377: Add parameter definition and translation for "enable-gfx".

guacamole-ext/src/main/resources/org/apache/guacamole/protocols/rdp.json

@@ -254,6 +254,11 @@
         {
             "name" : "performance",
             "fields" : [
+                {
+                    "name"    : "enable-gfx",
+                    "type"    : "BOOLEAN",
+                    "options" : [ "true" ]
+                },
                 {
                     "name"    : "enable-wallpaper",
                     "type"    : "BOOLEAN",

guacamole/src/main/frontend/src/translations/en.json

@@ -490,6 +490,7 @@
         "FIELD_HEADER_ENABLE_DRIVE"               : "Enable drive:",
         "FIELD_HEADER_ENABLE_FONT_SMOOTHING"      : "Enable font smoothing (ClearType):",
         "FIELD_HEADER_ENABLE_FULL_WINDOW_DRAG"    : "Enable full-window drag:",
+        "FIELD_HEADER_ENABLE_GFX"                 : "Enable Graphics Pipeline Extension (RemoteFX):",
         "FIELD_HEADER_ENABLE_MENU_ANIMATIONS"     : "Enable menu animations:",
         "FIELD_HEADER_DISABLE_BITMAP_CACHING"     : "Disable bitmap caching:",
         "FIELD_HEADER_DISABLE_OFFSCREEN_CACHING"  : "Disable off-screen caching:",