Revert "[JITLink] Fix some C++17 related fixmes."

This reverts commit 6ea5bf43.

6ea5bf43 made use of new c++17 rules regarding
order of evaluation (specifically: in function calls the expression naming the
function should be sequenced before the evalution of any operands) to simplify
some continuation-passing calls. Unfortunately this appears to break at least
one MSVC bot: https://lab.llvm.org/buildbot/#/builders/123/builds/12149 .

Includes an update to the comments to note that the workaround is now based on
MSVC limitations, not on LLVM adopting c++17.