Performance Improvements

Pass theme list & its entries around by reference rather than copying them.
Fix bug in async icon loading that caused icons to be loaded multiple times.

Original PR by @LiquidFenrir

include/unicode.h

@@ -29,9 +29,9 @@
 
 #include "common.h"
 
-ssize_t strulen(const u16*, ssize_t);
-void struacat(u16 *input, const char *addition);
-void printu(u16 *input);
-u16 *strucat(u16 *destination, const u16 *source);
+ssize_t strulen(const u16 *, ssize_t);
+void struacat(u16 * input, const char * addition);
+void printu(u16 * input);
+u16 * strucat(u16 * destination, const u16 * source);
 
 #endif