Disable ligatures by default. Performance sucks using core text and I don't...

Disable ligatures by default. Performance sucks using core text and I don't see a way to improve it without using all kinds of private APIs. The only difference I can find between us and Terminal is that they have a very flat view hierarchy. They don't use NSScrollView. I can't ditch NSScrollView because I can't cobble together a frankenstein from its parts the way Apple can.

sources/iTermProfilePreferences.m

@@ -244,8 +244,8 @@ NSString *const kProfilePreferenceInitialDirectoryAdvancedValue = @"Advanced";
                   KEY_BLINKING_CURSOR: @NO,
                   KEY_USE_BOLD_FONT: @YES,
                   KEY_THIN_STROKES: @(iTermThinStrokesSettingRetinaOnly),
-                  KEY_ASCII_LIGATURES: @YES,
-                  KEY_NON_ASCII_LIGATURES: @YES,
+                  KEY_ASCII_LIGATURES: @NO,
+                  KEY_NON_ASCII_LIGATURES: @NO,
                   KEY_USE_BRIGHT_BOLD: @YES,
                   KEY_BLINK_ALLOWED: @NO,
                   KEY_USE_ITALIC_FONT: @YES,