Cleanup: use term init instead of initialize/initialise

The abbreviation 'init' is brief, unambiguous and already used
in thousands of places, also initialize is often accidentally
written with British spelling.

intern/guardedalloc/MEM_guardedalloc.h

@@ -213,7 +213,7 @@ extern const char *(*MEM_name_ptr)(void *vmemh);
 
 /** This should be called as early as possible in the program. When it has been called, information
  * about memory leaks will be printed on exit. */
-void MEM_initialize_memleak_detection(void);
+void MEM_init_memleak_detection(void);
 
 /* Switch allocator to slower but fully guarded mode. */
 void MEM_use_guarded_allocator(void);

intern/guardedalloc/intern/leak_detector.cc

@@ -46,7 +46,7 @@ class MemLeakPrinter {
 };
 }  // namespace
 
-void MEM_initialize_memleak_detection(void)
+void MEM_init_memleak_detection(void)
 {
   /**
    * This variable is constructed when this function is first called. This should happen as soon as