[2.4] meson: with-lockfile-path options

[rdmark]

Backport from 3.2 the with-lockfile-path option to override the default lockfile / runstate dir.

Worth noting that this code changed a lot between 2.x and 3.x, so this is non-trivial to achieve. In 2.x, the lockfile paths are defined in include/atalk/paths.h inside preprocessor macros. As per the DEVELOPER readme, these macros can be overridden by a -D_PATH_LOCKDIR compiler flag. I'm going to attempt to wrap this in Meson to avoid touching the C code (don't want to have to make changes to Autotools for this.)