curl/types got removed in version 7.21.7 as it was not used. Attached ebuild patch sorts this out for version 5.0. Older versions are likely also affected but not tested by me.
Created attachment 280659 [details] build log
Created attachment 280661 [details, diff] firefox-5.0-r2.ebuild.patch
It is a duplicate of bug 375899.
*** This bug has been marked as a duplicate of bug 375899 ***