Nuke a dead field.

It looks like ex_temp_t.expr was never really used, and I have no idea
what I had intended (not surprising after ~17 years).

tools/qfcc/include/expr.h

@@ -91,7 +91,6 @@ typedef struct {
 } ex_block_t;
 
 typedef struct {
-	struct expr_s *expr;
 	struct operand_s *op;	///< The operand for the temporary variable, if
 							///< allocated
 	struct type_s *type;	///< The type of the temporary variable.

tools/qfcc/source/expr.c

@@ -426,7 +426,6 @@ copy_expr (expr_t *e)
 			*n = *e;
 			n->line = pr.source_line;
 			n->file = pr.source_file;
-			n->e.temp.expr = copy_expr (e->e.temp.expr);
 			return n;
 		case ex_vector:
 			n = new_expr ();