strptime(3) confused July with June with the fr_FR locale.

When parsing the month "juillet" (abbr "jul"), %B recognized it as
"juin" (abbr "jui") because the full name of the month names is
checked at the same time as the abbrevation.

The new behaviour checks the full names first before checking the
abbrevation names.

PR: kern/141939
Submitted by: Denis Chatelain <denis@tikuts.com>
MFC after: 1 week