Nvdxt can't be run multiple times at once

[adras]

pymapconv uses nvdxt.exe to convert images. While nvdxt is executed it creates a temp file: nvdxt_scratch.tmp. Therefore it's not possible to run nvdxt multiple times at once, because the file is already locked by the first process which is started.

Investigate:

• if it's possible to change the name of the temp file by parameter.
• Check out alternative tools