Define NOMINMAX on Windows
This will prevent the macro definition of min and max which breaks the use of std::min and std::max
We might have to fix one or two cases relying on a macro but we should get less cryptic errors than
00:11:11.302 C:/_/f4646fd0/kmime-21.04.3/src/kmime_headerfactory.cpp(37): error C2589: '(': illegal token on right side of '::'
00:11:11.302 C:/_/f4646fd0/kmime-21.04.3/src/kmime_headerfactory.cpp(37): error C2062: type 'unknown-type' unexpected
00:11:11.302 C:/_/f4646fd0/kmime-21.04.3/src/kmime_headerfactory.cpp(37): error C2059: syntax error: ')'