Crossport r984088 by tmcguire from trunk to the enterprise4 branch:

Speed up display of mails with many attachments, by introducing a cache in the code
that maps the mimetype to an icon name. The icon name was often not found, like for
image_jpeg, and that was slow.

According to the bug report, this improves message display from 20 to 3 seconds in some
cases.

Thanks to Martin for finding the reason for the speed problem.

CCBUG: 189961
CCBUG: 191666

svn path=/branches/kdepim/enterprise4/kdepim/; revision=986223