Correct printf parameter mismatch in wxWndProc.

Correct printf parameter mismatch in wxWndProc.

LPARAM is a 64 bit type in Win64 and doesn't match the size expected by "%l"
printf format specifier. Instead of showing it as a 32 bit number in 32 bit
build and 64 bit in 64 bits, just truncate it to the lower 32 bits in any case
for now, this should be enough for the diagnostic messages.

Closes #12242.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@65010 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775