remove some mozilla env variables

Change-Id: Ic0884c2e6a051a7767ac965a7daadfe64537b13d
no need for extern C here

Change-Id: I81a2af7aa5a52a0b19d05a64eacf89ed957a9ce8
that just looks wrong, related fdo#51935

And many more documents. Detected by the new asserts in the document
export code.

Change-Id: I207ab433b096c3cbaecf1b993595eb36e6553a5e