Open debugger at the location of failing assert, if possible.

Open debugger at the location of failing assert, if possible.

Break into the debugger in the function containing the assert that failed
instead of inside wxWidgets assert handler which is several (~8) levels below
the last line of the user code. This is much more useful in practice and also
less confusing.

Currently this only works for MSVC as the other compilers don't have any
__debugbreak intrinsice equivalent.

Also update the except sample to test wxTrap() directly too.

Closes #11184.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@73124 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775