argp: fix port of port new 'inline' approach to Sun C 5.12 + Solaris 10
The earlier patch forgot to update one of the #if conditions, causing
a problem on Debian testing i386 reported by Mats Erik Andersson
<http://lists.gnu.org/archive/html/bug-gnulib/2012-12/msg00124.html>.
* lib/argp-fmtstream.h (__argp_fmtstream_putc, argp_fmtstream_putc)
(__argp_fmtstream_puts, argp_fmtstream_puts)
(__argp_fmtstream_write, argp_fmtstream_write)
[!_LIBC && !__OPTIMIZE__]: Declare as ARGP_FS_EI, not as extern.