chore, turn off -Werror before checking mex header files

Signed-off-by: Sebastian Freundt <freundt@ga-group.nl>
minor, adapt gentexi.sh to cope with non-existing binaries and generate dummies instead

Signed-off-by: Sebastian Freundt <freundt@ga-group.nl>
chore, conditionalise on strptime for man generation

Signed-off-by: Sebastian Freundt <freundt@ga-group.nl>
Revert "chore, turn off -Werror before checking mex header files"

Reason is that we were using a feature that has been proposed to
upstream autoconf but hasn't been committed yet.

This reverts commit d60404737ef8d4d6970c420d6e11235b92667435.
chore, use good old SXE_LANG_WERROR to turn off -Werror handling after initial compiler checks

Signed-off-by: Sebastian Freundt <freundt@ga-group.nl>
Merge branch 'bld/dist' into next

* bld/dist:
  chore, use good old SXE_LANG_WERROR to turn off -Werror handling after initial compiler checks
  Revert "chore, turn off -Werror before checking mex header files"
  chore, conditionalise on strptime for man generation
  minor, adapt gentexi.sh to cope with non-existing binaries and generate dummies instead
  chore, turn off -Werror before checking mex header files