strip_colour: Strip '\x0F' (^O, formatting off)

Reported by ssbr on freenode:

chmode +c doesn't strip ^O, which turns off all previous formatting.
This can cause clients that internally use mIRC formatting to render messages weirdly,
e.g. highlighted messages in HexChat: <https://i.imgur.com/eDX8Aif.png>.
Merge branch 'master+umodes' of https://github.com/Adam-/charybdis
Merge branch 'patch-1' of https://github.com/auscompgeek/charybdis
server: Require EX and IE capabilities (+e and +I cmodes).

The code to send each channel mode only to servers supporting it was
broken a while ago and was not very useful anyway. Therefore, require
all connecting servers to support all standard channel modes.
channel: Stop pretending to support per-mode server capabilities.

After a change for dynamic server capabilities, the code to send out mode
changes was changed to use the capabilities belonging to the last mode
being sent out. This does not make sense; therefore, just use no
capabilities and remove supporting infrastructure.
channel: Remove write-only field.
configure: add --enable-shared-sqlite option

When --enable-shared-sqlite is used, charybdis will be compiled with a shared
sqlite library if it is available.
ircd_parser: Fix inconsistent declaration of yyerror().
bandb: make Makefile work with BSD make again
configure: use --with-shared-sqlite instead of --enable-shared-sqlite
configure: fix linking with shared sqlite on *BSD
configure: move local autoconf macros to m4/charybdis.m4
m4/pkg.m4: add pkg-config-0.24 macros
aclocal.m4: rerun aclocal
configure: use pkg-config for sqlite
Merge branch 'master+sharedsqlite' of https://github.com/lstarnes1024/charybdis