[Base] Test changing frequency to 49.875 instead of 50

Some public slides mention this is the actual frequency it runs at (slide 15: https://slideplayer.com/slide/9528088/)
KeQueryPerfFrequency always returns 50MHz though.

src/xenia/emulator.cc

@@ -119,8 +119,8 @@ X_STATUS Emulator::Setup(
   display_window_ = display_window;
 
   // Initialize clock.
-  // 360 uses a 50MHz clock.
-  Clock::set_guest_tick_frequency(50000000);
+  // 360 uses a ~49.875MHz clock.
+  Clock::set_guest_tick_frequency(49875000);
   // We could reset this with save state data/constant value to help replays.
   Clock::set_guest_system_time_base(Clock::QueryHostSystemTime());
   // This can be adjusted dynamically, as well.

src/xenia/kernel/xboxkrnl/xboxkrnl_threading.cc

@@ -283,8 +283,7 @@ void KeSetCurrentProcessType(dword_t type) {
 DECLARE_XBOXKRNL_EXPORT1(KeSetCurrentProcessType, kThreading, kImplemented);
 
 dword_result_t KeQueryPerformanceFrequency() {
-  uint64_t result = Clock::guest_tick_frequency();
-  return static_cast<uint32_t>(result);
+  return 50000000;  // always returns 50MHz, even though X360 is at 49.875 or so
 }
 DECLARE_XBOXKRNL_EXPORT2(KeQueryPerformanceFrequency, kThreading, kImplemented,
                          kHighFrequency);