PMD supports multiple languages. But most checks

are for java files only as the other languages

are for CPD only or requires manually added checks.
This features allows to increase the performance

of review checks as it is not necessary to run PMD

for all files in a diff if only .java has enabled

checks. Also this avoid but not fix bug #4633.
Also increase timeout as big patches with a lot

of files will take some time to be finished.
Fixes conflicting variable name 'f' introduced by

changeset f95629e2739037bd0e0f289875f710f2da4aa2dd

by mistake.

Added some binary files with another file extension

and saw that it wasn't scanned.
Enabled java extension only and added a java file.

Saw that the check found correct issues.
Leave the extension setting empty and saw that it

still found correct issues in uploaded java patch.
Used "cpp" as file extension and saw that it

ignores java files.