patch 8.1.0743: giving error messages is not flexible

Problem:    Giving error messages is not flexible.
Solution:   Add semsg().  Change argument from "char_u *" to "char *", also
            for msg() and get rid of most MSG macros. (Ozaki Kiichi, closes
            #3302)  Also make emsg() accept a "char *" argument.  Get rid of
            an enormous number of type casts.
diff --git a/src/proto/hardcopy.pro b/src/proto/hardcopy.pro
index 4791f4a..615f088 100644
--- a/src/proto/hardcopy.pro
+++ b/src/proto/hardcopy.pro
@@ -1,6 +1,6 @@
 /* hardcopy.c */
-char_u *parse_printoptions(void);
-char_u *parse_printmbfont(void);
+char *parse_printoptions(void);
+char *parse_printmbfont(void);
 int prt_header_height(void);
 int prt_use_number(void);
 int prt_get_unit(int idx);