start preparing to release SIMDe 0.8.4

prepare to release 0.8.0

prepare to release 0.8.0

 Add @thomas-schlichter as a contributor

arm/neon abs: negating INT_MIN is undefined behavior

- So cast to unsigned int before flipping sign, and then cast back to a signed int

LLVM 19 is making this more prominant: llvm/llvm-project#82112 (comment)
But this was already visible in earlier clang versions with `-O2` #901

- gh-actions: resume testing emscripten using the 'tip of tree' ("tot") builds.
- gh-actions: add clang-17 "-O2" build to confirm the fix

 Update @mr-c as a contributor

neon/cvtn: basic implementation of a few functions

Fixes: #1008

sse: remove unbalanced HEDLEY_DIAGNOSTIC_PUSH

Also cleanup some illegal double underscore variable names

Closes: #910

sve/true,whilelt,cmplt,ld1,st1,sel,and: skip AVX512 native implementa…

…tions on MSVC 2017

arm/neon/rnd: use correct SVML function for simde_vrndq_f64