0029171: Foundation Classes - C signal handler does not work on MinGW

0029171: Foundation Classes - C signal handler does not work on MinGW

Setting signal handler is enabled in OSD::SetSignal() for MinGW (works only for SEH builds of MinGW, not for SJLJ builds).

Due to absence of function _set_se_translator(), handler is set using C signal() function and thus is called asynchronously.
Macro OCC_CONVERT_SIGNALS is enabled for MinGW build to support converting signals to C++ exceptions using long jumps (the same as on Linux).
Code raising exceptions in OSD::SetSignal() is corrected to use method Jump() instead of C++ throw.