Improve code and clarify parameters to ABI_Push/PopRegistersAndAdjustStack.

- Factor common work into a helper function.
- Replace confusingly named "noProlog" with "rsp_alignment".  Now that
x86 is not supported, we can just specify it explicitly as 8 for
clarity.
- Add the option to include more frame size, which I'll need later.
- Revert a change by magumagu in March which replaced MOVAPD with MOVUPD
on account of 32-bit Windows, since it's no longer supported.  True,
apparently recent processors don't execute the former any faster if the
pointer is, in fact, aligned, but there's no point using MOVUPD for
something that's guaranteed to be aligned...

(I discovered that GenFrsqrte and GenFres were incorrectly passing false
to noProlog - they were, in fact, functions without prologs, the
original meaning of the parameter - which caused the previous change to
break.  This is now fixed.)
Remove the inaccurately named ABI_PushAllCalleeSavedRegsAndAdjustStack (it didn't preserve FPRs!) and replace with ABI_PushRegistersAndAdjustStack.

To avoid FPRs being pushed unnecessarily, I checked the uses: DSPEmitter
doesn't use FPRs, and VertexLoader doesn't use anything but RAX, so I
specified the register list accordingly.  The regular JIT, however, does
use FPRs, and as far as I can tell, it was incorrect not to save them in
the outer routine.  Since the dispatcher loop is only exited when
pausing or stopping, this should have no noticeable performance impact.
Remove ABI_AlignStack/ABI_RestoreStack and the noProlog option to ABI_CallFunctionRR.

The latter being true was the only case where the former would do
anything, and it was never true.  They became obsolete with x86's
removal.
Opportunistically predict BLR destinations using RET.

When executing a BL-type instruction, push the new LR onto the stack,
then CALL the dispatcher or linked block rather than JMPing to it.  When
executing BLR, compare [rsp+8] to LR, and RET if it's right, which it
usually will be unless the thread was switched out.  If it's not right,
reset RSP to avoid overflow.

This both saves a trip through the dispatcher and improves branch
prediction.

There is a small possibility of stack overflow anyway, which should
be handled... *yawn*
Shorten the blr stub a bit.
Run exception handlers on an alternate stack on Linux.

*Completely untested.*  Someone please test.
Reorganize backpatching a bit.  Untested on ARM.

Rather than *MemTools.cpp checking whether the address is in the
emulated range itself (which, as of the next commit, doesn't cover every
kind of access the JIT might want to intercept) and doing PC
replacement, they just pass the access address and context to
jit->HandleFault, which does the rest itself.

Because SContext is now in JitInterface, I wanted JitBackpatch.h (which
defines it) to be lightweight, so I moved TrampolineCache and associated
x64{Analyzer,Emitter} dependencies into its own file.  I hate adding new
files in three places, two of which are MSVC...
    Be pedantic about stack overflow.

    Add some magic to the fault handler to handle stack overflow
    due to BLR
    optimization, and disable the optimization if fastmem is
    not enabled.