make $lib_path configurable

[fraenki]

In conjunction with ${apache::apache_version} it is sometimes required to also change $lib_path to a non-default location. This patch introduces lib_path as a new parameter.

[igalic]

are those uses in mod_wsgi and mpm the only ones?
should we generally make this a template for modules?

[bmjen]

Please add a test for the new param.

[cmurphy]

I don't think there's an especially obvious place to add a test for this, and I'd be fine with going without. I would still like to see @igalic's questions answered.

[underscorgan]

@fraenki ping?

[fraenki]

@igalic These are the only occurences of ::apache::params::lib_path. I don't think there's more to do here, since this is a somewhat special use-case.
@mhaskel Sorry for my late reply. :-(