util_get_directory_variants

The main_path is a directory, which will be always used.

It should have as its prefix the replace_prefix, otherwise the function returns only the main_path in the paths array.

When there's exported an environment variable EDS_EXTRA_PREFIXES, it is used as a list of alternative prefixes where to look for the main_path (rest after the replace_prefix).

When the with_modules_dir is true, there's also added get_user_data_dir + "evolution/modules/", aka ~/.local/share/evolution/modules/, into the resulting array.

Parameters:

main_path	the main path to work with
replace_prefix	path prefix to replace
with_modules_dir	whether to add also the modules directory

Returns:

a gptrarray with paths to use, including the main_path. Free it with g_ptr_array_unref, when no longer needed.