regexp: OOM when compiling nested x{n}

<pre>What does 'go version' print?
go version devel +3ca54dd30864 Sat Mar 22 11:05:40 2014 -0700 linux/amd64

What steps reproduce the problem?
Go process is killed while compiling `(?:(?:x{1,1000}){1,1000}){1,1000}` because of OOM
error. It consumes more than a few gigs of RAM before it dies.
<a href="http://play.golang.org/p/xI70NqvfIo">http://play.golang.org/p/xI70NqvfIo</a></pre>
