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.
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