winecfg: Update the drives only when they have changed, instead of trying to compare with the current setup.

configure: Explicitly mention that we need 32-bit libraries to try to avoid some invalid bug reports.

For some reason EM_POSFROMCHAR was returning 0 when the position was
equal to the end of the text, or beyond the end of the text. Instead
it should use the position at the end of the text for both these
cases.  The x value was also seen to be offset by 1 according to the
tests.

This makes applications with custom callbacks work properly, and fixes
'make test' in a win9x mode.