#36 add DivU64x32 assembly definition for MinGW on ia32

[Pete Batard]

The default __GNUC__ C code cannot be used with MinGW as it inserts implicit calls to _umoddi3 and _udivdi3, which are unavailable when compiling without the standard libraries (-nostdlib).

This patch addresses this by providing an inline assembly definition that is an exact conversion of the existing MS one, but for GCC's AT&T syntax.

PS: Many thanks for applying all these recent patches!
I think this should be the last one I need for the time being...

[Nigel Croxon]

fixed in commit 78e4df7c5e506f9a9a21207a8e320865438e02ec

Many thanks in return for fixing issues and making them right.