OpenDir performance: Read DirIV once and reuse it for all names

Formerly, we called decryptPath for every name.
That resulted in a directory walk that reads in all diriv files
on the way.

Massive improvement for RM and LS (check performance.txt for details)

VERSION         UNTAR   RM   LS
v0.4               48    5    1.5
v0.5-rc1           56   19    7
v0.5-rc1-1         54    9    4.1   <---- THIS VERSION

0 files changed, 0 insertions, 0 deletions