Store the initializer expression in the def.

Initially, this will be used for collecting the targets of a jumpb
instruction.

tools/qfcc/include/def.h

@@ -44,6 +44,7 @@ typedef struct def_s {
 
 	struct def_s   *alias;
 	struct reloc_s *relocs;			///< for relocations
+	struct expr_s  *initializer;	///< initialer expression
 
 	unsigned		offset_reloc:1;	///< use *_def_ofs relocs
 	unsigned		initialized:1;

tools/qfcc/source/def.c

@@ -527,4 +527,5 @@ initialize_def (symbol_t *sym, type_t *type, expr_t *init, defspace_t *space,
 			sym->s.def->nosave = 1;
 		}
 	}
+	sym->s.def->initializer = init;
 }