MFC r299778:

MFC r299778:

Use a consistent errno save/restore pattern before running strtoul

- Save errno
- Set errno to 0
- Call strtoul
- Test errno (optional, but many calls to strtoul did this afterwards)

Some of the code was setting errno = 0 after calling strtoul, not setting
errno = 0, or setting errno to saved_errno after the call, but before the
test. These all have unwanted behavioral side-effects, depending on the
initial value of errno and whether or not the input to strtoul was correct
or incorrect.

git-svn-id: svn://svn.freebsd.org/base/stable/10@301656 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f