newsyslog: treat 'c' flag in the config as 'C'

When -C was introduced in r114137 the plan was to have -C and -c being used for
"create" due to a typo in FreeBSD <= 4.8 a temporary compatibility hack has been
added to make -c being like -G aka GLOB and a warning was issued for the user to
be aware of the futur change for -c.

12 years later it is more than time to remove that hack and finish the what was
intent in r114137

Submitted by: Alexandre Perrin <alex@kaworu.ch>
Relnotes: yes
Differential Revision: https://reviews.freebsd.org/D4000