Automatically disable fastmem and enable memcheck when there are any watchpoints.

- Move JitState::memcheck to JitOptions because it's an option.
- Add JitOptions::fastmem; switch JIT code to checking that rather than
  bFastmem directly.
- Add JitBase::UpdateMemoryOptions(), which sets both two JIT options
  (replacing the duplicate lines in Jit64 and JitIL that set memcheck
  from bMMU).
  - (!) The ARM JITs both had some lines that checked js.memcheck
    despite it being uninitialized in their cases.  I've added
    UpdateMemoryOptions to both.  There is a chance this could make
    something slower compared to the old behavior if the uninitialized
    value happened to be nonzero... hdkr should check this.
- UpdateMemoryOptions forces jo.fastmem and jo.memcheck off and on,
  respectively, if there are any watchpoints set.
- Also call that function from ClearCache.
- Have MemChecks call ClearCache when the {first,last} watchpoint is
  {added,removed}.

Enabling jo.memcheck (bah, confusing names) is currently pointless
because hitting a watchpoint does not interrupt the basic block.  That
will change in the next commit.

Source/Core/Common/BreakPoints.h

@@ -105,6 +105,8 @@ public:
 	void Remove(u32 _Address);
 
 	void Clear() { m_MemChecks.clear(); }
+
+	bool HasAny() const { return !m_MemChecks.empty(); }
 };
 
 class Watches