...and initializing it on-demand in SvNumberFormatter::ImpGenerateFormats wasn't
even thread safe (despite theIndexTable.maMtx):  While one thread was cleaning
and then filling it in ImpGenerateFormats, another thread could also enter
ImpGenerateFormats and clean it again (and only later fill it), and the first
thread might use the half-filled table after it left ImpGenerateFormats but
before the second thread re-filled it.

Change-Id: Iba4e9d57519d2b288718b9cb2e6f7546ba2bd5df