turn a few #include paths from the "foo" form to <foo>

turn a few #include paths from the "foo" form to <foo>

The quotes form is normally only used for headers with path relative
to the including file's path, though the standard doesn't strictly
mandate this. This is consistent with the rest of sg/fg, it makes the
code's intent clearer and helps to find headers. (And it's a few
milliseconds faster, too.)