hal: add stub module that loads module-udev-detect instead of module-hal-detect

hal: add stub module that loads module-udev-detect instead of module-hal-detect

This adds module-hal-detect-compat.c which when enabled will be compiled
into a module module-hal-detect which simply loads module-udev-detect.

The purpose of this is to allow easy upgrading without breaking
default.pa. Distributions are recommended to enable this to easy
upgrades from HAL versions of PA to udev versions.