newline handling

In light of the recent 'bad options' feedback issue where \r messed
up message display, try to to make newline handling be more consistent.
I'm sure there are lots of places that still handle \n manually, but
it's a start.

include/extern.h

@@ -835,6 +835,7 @@ E char *FDECL(lcase, (char *));
 E char *FDECL(ucase, (char *));
 E char *FDECL(upstart, (char *));
 E char *FDECL(mungspaces, (char *));
+E char *FDECL(strip_newline, (char *));
 E char *FDECL(eos, (char *));
 E boolean FDECL(str_end_is, (const char *, const char *));
 E char *FDECL(strkitten, (char *, CHAR_P));