[testsuite] Get rid of dg-skip-if etc. default args

[Mike Stump]

On Jun 15, 2017, at 3:49 PM, Rainer Orth <ro@CeBiTec.Uni-Bielefeld.DE> wrote:
> 
> It has long bothered me that many calls to dg-skip-if and its companions
> dg-xfail-if and dg-xfail-run-if in the testsuite are cluttered with the
> unnecessary default arguments ({ "*" } { "" } with and without braces).

> Now, this patch removes them wholesale.

Sounds good to me.