const const const

adding hints for the compiler for optimization.
In case your custom build complains about "const", just remove the keyword. based on e82f38e277, but going further :-)

* "const" class functions : function does not modify any class attributes ( --> "this" becomes const)

* __attribute__((pure)) :  function return value depends only on the parameters and/or global variables. The function does not modify any global or static variables.
* __attribute__((const)) : function only examines arguments (no globals), and has no effects except the return value. This slightly more strict than "pure"
* hot: tells the compiler "this functions is called very often"
* cold: the opposite of hot

wled00/src/dependencies/time/TimeLib.h

@@ -116,7 +116,7 @@ char* dayShortStr(uint8_t day);
 
 /* low level functions to convert to and from system time */
 void breakTime(time_t time, tmElements_t &tm);  // break time_t into elements
-time_t makeTime(tmElements_t &tm);  // convert time elements into time_t
+time_t makeTime(tmElements_t &tm) __attribute__((pure));  // convert time elements into time_t
 
 } // extern "C++"
 #endif // __cplusplus