Fix a few typos in comments

Apply the following spelling fixes:
$ git grep -F -l 'relevent' |
  xargs sed -i 's/relevent/relevant/g'
$ git grep -F -l 'checked fot' |
  xargs sed -i 's/checked fot/checked for/g'
$ git grep -F -l "could't" |
  xargs sed -i "s/could't/couldn't/g"
$ git grep -F -l 'wheter' | grep -Fv ChangeLog.old |
  xargs sed -i 's/wheter/whether/g'
$ git grep -F -l 'neccessary' | grep -Fv ChangeLog.old |
  xargs sed -i 's/neccessary/necessary/g'
$ git grep -F -l 'ouput' |
  xargs sed -i 's/ouput/output/g'
$ git grep -F -w -l 'iput' |
  xargs sed -i 's/iput/input/g'

This is inspired by a gnulib bug report at
https://lists.gnu.org/archive/html/bug-gnulib/2019-01/msg00081.html

* argp/argp-help.c: Fix typo in comment.
* misc/sys/cdefs.h: Likewise.
* posix/regexec.c (sift_states_iter_mb): Likewise.
* socket/sockatmark.c: Likewise.
* socket/sys/socket.h: Likewise.
* sysdeps/ia64/fpu/libm_sincos_large.S: Likewise.
* sysdeps/ia64/fpu/libm_sincosl.S: Likewise.
* sysdeps/ia64/fpu/s_cosl.S: Likewise.
* sysdeps/ieee754/dbl-64/k_rem_pio2.c: Likewise.
* sysdeps/unix/sockatmark.c: Likewise.
* time/strptime_l.c: Likewise.

1 files changed, 1 insertions, 1 deletions

diff --git a/posix/regexec.c b/posix/regexec.c
index 0a7a27b772..91d5a797b8 100644
--- a/posix/regexec.c
+++ b/posix/regexec.c
@@ -2207,7 +2207,7 @@ sift_states_iter_mb (const re_match_context_t *mctx, re_sift_context_t *sctx,
 			    dfa->nexts[node_idx]))
     /* The node can't accept the "multi byte", or the
        destination was already thrown away, then the node
-       could't accept the current input "multi byte".   */
+       couldn't accept the current input "multi byte".   */
     naccepted = 0;
   /* Otherwise, it is sure that the node could accept
      'naccepted' bytes input.  */