Bring r22180, r22181 and r22214 from trunk to 1.8 branch:
Add new "metadata block size" command line option ('-M <x>' or
'--metadata_block_size=<x>') for h5repack.
[With release managers blessing]
Tested on:
Mac OSX/64 10.7.3 (amazon) w/debug)
(h5committest upcoming)