Change the syntax to include parameter names and a trailing semicolon.
Motivation:
- Mirror the `syscall!` macro.
- Allow rustfmt to format it (when wrapped in parentheses).
- For better documentation (having the parameter names available in
the source code is a bit nicer).
- Allow future improvements to this macro where we can sometimes use the
symbol directly when it's statically known to be available.
a7bafc0afc