regexp: re-enable TestBadCompile
regexp: re-enable TestBadCompile

The code that was commented out was for the old regexp package.
In the new one the errors and the space of valid regexps are different.

R=golang-dev, bradfitz
CC=golang-dev
https://codereview.appspot.com/6873063

wesolows/golang,wesolows/golang,wesolows/golang-old,wesolows/golang-old,firebitsbr/golang-old,wesolows/golang-old,wesolows/golang,firebitsbr/golang-old,firebitsbr/golang-old,wesolows/golang,firebitsbr/golang-old,firebitsbr/golang-old,wesolows/golang,wesolows/golang-old,wesolows/golang-old,firebitsbr/golang-old,firebitsbr/golang-old,wesolows/golang-old,firebitsbr/golang-old,wesolows/golang-old,wesolows/golang,wesolows/golang