Free memory used by optimization/target options

[Jan Hubicka]

> On Tue, 5 Nov 2019, Jan Hubicka wrote:
> 
> > Hi,
> > this fixes memory leak for xstrduped strings in option summaries which may
> > get ggc_freed by tree merging.
> > 
> > Bootstrapped/regtested x86_64-linux, OK?
> 
> OK.  If those are ever reaped by regular GC the memory still leaks, no?
> So wouldn't it be better to put the strings into GC memory?
I am not sure why those are malloced, but I think there was some fun
with gengtype/awk generator interactions. Also I think all those option
nodes come into cl_option_hash that is fully permanent.

Honza