* libc/unix/ttyname.c: Remove ttyname_r() (to a new file to avoid
coupling ttyname_r() and ttyname() due to the latter's large buffer).
* libc/unix/ttyname_r.c: New file to hold ttyname_r(), previously in
ttyname.c.
* libc/unix/ttyname.h: New file (common size definition for the 2
ttyname*c files that are now split).
* libc/unix/Makefile.am (ELIX_2_SOURCES): Add ttyname_r.c.
* libc/unix/Makefile.in: Regenerate.