Add code to test encryption and export to .docx on iOS

Conditional on the environment variable
PTYL_TEST_ENCRYPTION_AND_EXPORT, eek. The document is written out
using the name of the input document with .new.docx appended.

I placed the function that handles it, somewhat arbitrarily, in
sofficemain.cxx. The invocation of this function is, also somewhat
arbitrarily, placed in TiledView's drawLayer:inContext: method.

Quite possibly this test functionality occasionally causes solar mutex
deadlocks or whatever, but at least in Xcode, when one has placed some
breakpoints in it, it seems to work. Which is what matters, as this is
code for manual testing, not invoked normally.

Change-Id: I38bb4b406edf47f0f24857b6044e3bf4eaf17c34