Disable fromFloat32x4 and fromInt3x4 for now

Odin doesn't yet support these functions, so disable them for now
to allow validation to succeed
update cashew
accept 'cleanup' as a native optimizer-friendly pass
convert asmLastOpts to native optimizer
add test for asmLastOpts without last
asmLastOpts fixes
update cashew
enable asmLastOpts to native optimizer
fix nasty little bug in Module.ccall
Merge pull request #3028 from NWilson/ccall_fix

fix nasty little bug in Module.ccall
fix docs link; fixes #3026
Add pthread-related attr code from musl 1.0.3.
Fix syntax error in a_cas_p of musl/arch/js/atomic.h
Add a few more musl pthread functions.
Don't run memory initializer when starting up a pthread, since the same static memory area is shared with the main thread and is therefore already initialized when the pthread starts up.
Remove the tempDoublePtr memory allocation for pthreads. TODO: Once memory allocation is thread-safe, make this available for pthreads.
Remove memory allocation for filesystem for pthreads since it is not yet thread-safe. Remove the previous stub pthread symbols in library.js to make room for the new pthread implementation.
Remove the pthread_cleanup_push/pop macros in musl pthread.h, since we need to call to JS for pthread cleanup implementation.
Remove some currently unused headers from being included in musl for Emscripten.
Add a w.i.p. mechanism to distinguish between running as a secondary pthread, and running the main thread as a worker with -s PROXY_TO_WORKER.