• Display a stage-qa warning when ports use PREFIX/var instead of /var
• Add --localstatedir=/var to _LATE_CONFIGURE_ARGS (like --mandir) but not when CONFIGURE_ARGS already sets it. (GNU configure scripts set it to PREFIX/var when PREFIX != /usr.)
• Add --localstatedir="${PREFIX}/var" to CONFIGURE_ARGS in some ports so they aren't affected by this change (for now at least). This commit is meant to ensure that new ports don't make the same mistake.

• games/acm: the configure script in this port is very old; instead of patching it more, just replace GNU_CONFIGURE with HAS_CONFIGURE.
• irc/charybdis: it already used /var but adding --localstatedir=/var changed the behaviour of the configure script; adjust the port to this.

PR: 199506
Exp-run by: antoine
Approved by: portmgr (antoine)