Add missing headers

[pastalian]

Some systems must explicitly include these headers.

Reported by: https://bugs.gentoo.org/922263

/var/tmp/portage/games-emulation/rpcs3-9999/work/rpcs3-9999/Utilities/Thread.cpp:3135:17: error: use of undeclared identifier 'SYS_gettid'
 3135 |         return syscall(SYS_gettid);

/var/tmp/portage/games-emulation/rpcs3-9999/work/rpcs3-9999/Utilities/JITASM.cpp:23:52: error: use of undeclared identifier 'getpid'; did you mean 'getpt'?
   23 |                 std::string name{fmt::format("/tmp/perf-%d.map", getpid())};
      |                                                                  ^~~~~~
      |                                                                  getpt

/var/tmp/portage/games-emulation/rpcs3-9999/work/rpcs3-9999/3rdparty/GL/../pine/pine_server.h:433:24: error: use of undeclared identifier 'read'; did you mean '_IO_cookie_io_functions_t::read'?
  433 |                                         auto tmp_length = read_portable(m_msgsock, &m_ipc_buffer[receive_length], MAX_IPC_SIZE - receive_length);

[MSuih]

You could just do #ifndef MSVC or #ifndef _WIN32 at this point

[pastalian]

sure

[pastalian]

Wait, it's right above this. Why was this even separated lol.

[kd-11]

Since it's a platform check, _WIN32 would be the right define to check for.