Log Message:
Update p5-MMapDB to 0.15.

Changes from previsou:
----------------------
0.15  Mon Sep 10 10:37:44 CEST 2012
      - make "map {local $_} values %{$d->main_index}" work
        map creates an alias ($_) and local tries to assign to it.
        Prior this threw an exception.

0.14  Sun Apr  3 20:57:57 CEST 2011
      - index_lookup and index_lookup_position now accept 0 or undef in
      	place of the index parameter. In this case the mainidx is looked up.
	Should be a bit faster than passing $db->mainidx.
      - index_lookup_records(), index_lookup_values(), index_lookup_sorts()
      - speed up writing: mmap _tmpfh and _stringfh to avoid sysseek+syswrite

        v0.13: 20.7612 (19.09 usr +  1.63 sys = 20.72 CPU) @  1.06/s (n=22)
        v0.14: 20.299 (20.20 usr +  0.05 sys = 20.25 CPU) @  1.68/s (n=34)
                Rate v0.13 v0.14
        v0.13 1.06/s    --  -37%
        v0.14 1.68/s   58%    --

0.13  Thu Mar 31 12:27:39 CEST 2011
      - MMDB-lookup tool
      - data_record, data_value and data_sort now work on a position list
        instead of a single position.

0.12  Sun Oct 31 14:22:53 CET 2010
      - fixed subtle UTF8 problem: 2 strings consisting of the same ascii
      	characters were considered different if one of them had the UTF8
	flag set while the other had not.

	Example:

	  no utf8;      # just to make sure
	  Encode::decode_utf8('hello') eq 'hello'

	In Perl this is true. The MMapDB index_lookup function reported them
	as different up to version 0.11.

0.11  Sat Jun  5 16:37:48 CEST 2010
      - removed _rwdata, since File::Map provides protect() now (since 0.21)
      - avoid lvalue substr() in invalidate since this prevents the
        file map to be destroyed in time.

0.10  Fri May 14 13:58:13 CEST 2010
      - make references to the MMapDB object from MMapDB::_base objects
        (tied interface) weak.

0.09  Mon May  3 19:54:25 CEST 2010
      - declare @attributes as 'our'
      - data_value, data_sort accessors
      - DATAMODE_SIMPLE
      - untie in stop() to break circular refs