Removed IPlug from WDL -- from 37d134e2

Note: if you are merging into another IPlug repository, you should ignore
this commit.

Recommended IPlug forks:

https://github.com/olilarkin/wdl-ol
http://www.taletn.com/WDL.git

If you would like the last IPlug version that we (Cockos) hosted, we have
the branch: deprecated_iplug
SWELL: reduced use of lstrcpyn internally, use wdlcstring.h instead -- from 06c2e27f