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/argp/argp-help.c b/argp/argp-help.c
index 0ccd012084..52ec2316fa 100644
--- a/argp/argp-help.c
+++ b/argp/argp-help.c
@@ -1540,7 +1540,7 @@ argp_doc (const struct argp *argp, const struct argp_state *state,
 }
 
 /* Output a usage message for ARGP to STREAM.  If called from
-   argp_state_help, STATE is the relevent parsing state.  FLAGS are from the
+   argp_state_help, STATE is the relevant parsing state.  FLAGS are from the
    set ARGP_HELP_*.  NAME is what to use wherever a `program name' is
    needed. */
 static void