GCC and CLang compilers fail to support full IEC559 compliance required for the test, when certain compiler flags are active. This patch implements a heuristic that checks for the most common flag in GCC and CLang, plues an extra check which GCC disables when it's not compliant, to hopefully catch most cases where it can't run.
Multiplying by a factor of 1/1000.f (rather than dividing by 1000.f) directly
introduces an error of 1 ULP. With this patch, an exact comparison of a
floating point literal with the deserialized F1000 form representing it is now
guaranteed to be successful.
In addition, the maxmium and minimum safely representible floating point
numbers are now well-defined as constants.
Use wide_to_utf8 and utf8_to_wide instead of wide_to_narrow and narrow_to_wide at almost all places.
Only exceptions: test functions for narrow conversion, and chat, which is done in a separate commit.
