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Previously, a number of errors were contructed as automatic variables then returned to the caller - potentially accessing stale stack area. All error blocks are now held in ROM and cast from there.
Error numbers are now not &00000000 or &20202020, using the allocated base - requires 'Common-0_15'.
Trimmed some unused debugging code out, saves about 3k.
Renamed C++ clashing variables to stop the compiler moaning.
Implemented feature request to accept the empty string "" as no font handle in _SetFont calls.
At some point, this module needs internationalising.

Version 0.31. Tagged as 'Gadgets-0_31'