Jit64: implement tw/twi more accurately

Fixes issue 7253.
Apparently the debug build has not been freeing memory since 2008. Undo that.
Merge pull request #352 from shuffle2/master

[windows] Fix debug build memory leaks.
Revert "x64FPURoundMode: always set x87 precision"

This reverts commit 9de77b7c23252cbedaee993f7c56b2deb0ce2bef.
Setting x87 precision control is only supported on x86 platforms (not ARM or x64).
Merge pull request #335 from Tilka/twx

Jit64: implement tw/twi more accurately
Merge pull request #357 from shuffle2/master

Revert "x64FPURoundMode: always set x87 precision"
Opcode decoding: handle missing opcodes 0x88 etc.

Hardware testing shows that they do the same thing as the 0x80 family of
opcodes: they draw quads.