libxl: remove comment support from IDL

libxl: remove comment support from IDL

People typically don't look for comments in generated source and the syntax for
specifying them in the IDL makes things harder to follow.

Instead just use source code comments in the IDL itself.

I dropped a bunch of "foo bool # enable or disable foo" type comments. A lot of
the remainder still aren't terribly useful though.

No change to the generate code other than the comments being removed.

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
Acked-by: Ian Jackson <ian.jackson@eu.citrix.com>
Committed-by: Ian Jackson <Ian.Jackson@eu.citrix.com>