64-bit support

[thecybermind]

IOQuake provides 64bit support and 64-bit compilations of the default baseq3 and missionpack mod files.

Most of the changes will involve using intptr_t for arguments instead of int. For QVM, the only real change (since the QVMs are compiled as "32-bit" all the time), is to copy the args into an intptr_t array before passing to Q3A_vmsyscall (See https://github.com/ioquake/ioq3/blob/main/code/qcommon/vm_interpreted.c#L504 )

[thecybermind]

Following ioquake3, I have switched all API types from int to intptr_t except inside QVMs, but it performs conversions to/from int when going in/out of the virtual machine.

I have also added 64-bit support to the MSVC project and linux makefile.

I was able to test Q3A 64-bit along with 64-bit versions of stub_qmm and rocketmod_qmm plugins.