Revert "ODS load perf: accelerate CompileXML for formula by stringify and...

...compare."

This reverts commit 4a5d600a0ab8b851bd7565e36be3419066145908 (plus follow-up
8400f1092d2ac38ff0570837957250f45c6e156d "ODS load perf: remove left-over /
debugging getenv").  It causes crashes due to stale heap access in
CppunitTest_sc_subsequent_filters_test etc. when ScFormulaCell::CompileXML first
calls SetCellGroup, which deletes pCode, and then calls aComp.CompileTokenArray,
where aComp has earlier been instantiated on *pCode and now calls GetCodeError
on it.

Change-Id: I9c86d26604b2895e92dce38611a1f8d1f099494d