pathspec: copy and free owned memory

pathspec: copy and free owned memory

The 'original' string entry in a pathspec_item is only duplicated some
of the time, instead always make a copy of the original and take
ownership of the memory.

Since both 'match' and 'original' string entries in a pathspec_item are
owned by the pathspec struct, they need to be freed when clearing the
pathspec struct (in 'clear_pathspec()') and duplicated when copying the
pathspec struct (in 'copy_pathspec()').

Also change the type of 'match' and 'original' to 'char *' in order to
more explicitly show the ownership of the memory.

Signed-off-by: Brandon Williams <bmwill@google.com>
Reviewed-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>