Fixes another problem with JSNI method signatures introduced in r2090.  Decided to maintain information about whether a type bound was implicit (i.e. ?) or explicit ? (extends | super) T.

Added a test case to JWildcardTypeTest to make sure that we don't break JSNI again.

Review by: spoon (desk check)

git-svn-id: https://google-web-toolkit.googlecode.com/svn/trunk@2110 8db76d5a-ed1c-0410-87a9-c151d255dfc7