Use checked pointers in all function replacements.

Some games are still hitting bugs and there's no way to disable this "fast
memory" without losing graphical effects.  Better to do it evenly than
weird hacks and extra logging/checks.
Disable a bunch of function replacements.

These are just for speed, let's turn them off.  Using a flag because:
 * I think there's still some issue with savestates, not sure.
 * We might swap this flag to a separate option.
Use a lookup for function replacements.

Ought to be a tiny bit quicker.
Don't zero out downcount in replacements.

It doesn't write out js.downcountAmount in any of these cases, so zeroing
it is wrong.
Wrong permission in jpn0.pgf. It should have the same as other files (-rw-rw-r--).
Merge pull request #6684 from sergiobenrocha2/master

Wrong permission in jpn0.pgf. It should have the same as other files (-rw-rw-r--).
Use glStencilMask() to partially simulate amask.

Alpha won't be correct, though.
Update native
Merge branch 'stencil-mask' of github.com:unknownbrackets/ppsspp into unknownbrackets-stencil-mask
Merge branch 'unknownbrackets-stencil-mask'
Merge pull request #6680 from unknownbrackets/replace-funcs

Disable most replacements and use checked mem access in them
Use correct stencil values with non-add blending.

Otherwise, we get the min/max/etc. value instead.
Also do it here, although may be removed soon.
Note the location of a memset variant.
Premultiply for doubled alpha blending if possible.

This makes the effect more accurate where the values were being clamped
before.  Some obscure methods of blending may be slower.
Avoid recalculating replaceBlend so many times.
Avoid premultiplying easy fixed colors.
Dirty the fixed color when premultiplying.
Avoid using fbo copies for the common 2a + 1-2a.

We won't even get it right that often since the copy doesn't deal with
overlap properly.
Improve a possible obscure blend mode.

Seems like this would be likely to get overlap problems.