Spelling fixes in comments and descriptions, patch by luzpaz.

Differential Revision: https://developer.blender.org/D3732

source/blender/editors/interface/interface_utils.c

@@ -120,7 +120,7 @@ uiBut *uiDefAutoButR(uiBlock *block, PointerRNA *ptr, PropertyRNA *prop, int ind
 				but = uiDefButR_prop(block, UI_BTYPE_TEXT, 0, name, x1, y1, x2, y2, ptr, prop, index, 0, 0, -1, -1, NULL);
 
 			if (RNA_property_flag(prop) & PROP_TEXTEDIT_UPDATE) {
-				/* TEXTEDIT_UPDATE is usally used for search buttons. For these we also want
+				/* TEXTEDIT_UPDATE is usually used for search buttons. For these we also want
 				 * the 'x' icon to clear search string, so setting VALUE_CLEAR flag, too. */
 				UI_but_flag_enable(but, UI_BUT_TEXTEDIT_UPDATE | UI_BUT_VALUE_CLEAR);
 			}