tag: converted tag_item.value to a char array

The value is stored in the same memory allocation as the tag_item
struct; this saves memory because we do not store the value pointer
anymore.  Also remove the getTagItemString()/removeTagItemString()
dummies.

src/tagTracker.h

@@ -19,10 +19,6 @@
 #ifndef TAG_TRACKER_H
 #define TAG_TRACKER_H
 
-char *getTagItemString(int type, char *string);
-
-void removeTagItemString(int type, char *string);
-
 int getNumberOfTagItems(int type);
 
 void printMemorySavedByTagTracker(void);