Massage code for clang-format

Massage code for clang-format

This change starts the process of updating the jit code to make it ready
for being formatted by clang-format. Changes mostly include reflowing
comments that go past our column limit and moving comments around ifdefs
so clang-format does not modify the indentation. Additionally, some
header files are manually reformatted for pointer alignment and marked
as clang-format off so that we do not lose the current formatting.

Commit migrated from https://github.com/dotnet/coreclr/commit/a1fa8c14cae981369dccf2f361b01959b215ad8f