Fix a potential memory leak in filelist creation
If we begin to create a file list when loading a package, but abort
because of an error to one of our goto labels, the memory used to create
the file list will leak. This is because we use a set of local variables
to hold the data, and thus _alpm_pkg_free() cannot clean up for us.
Use the file list struct on the package object as much as possible to
keep state when building the file list, thus allowing _alpm_pkg_free()
to clean up any partially built data.
Signed-off-by: Dan McGee <dan@archlinux.org>