Research whether C inline ASM functions change compiler settings

[ghost]

@riidefi mentioned in #31 that asm void-style functions have been suspected to change compiler flags, affecting the way how other / unrelated code in the same TU would be compiled.

We could wrap inline ASM functions in push/pop pragmas to backup and restore the compiler settings state as a workaround.

Before doing that, it would be nice to create a minimum code sample that reproduces this effect on known affected compiler version and check if it affects the one's we're using as well.