[extensions] Ignore query strings when checking for extensions.

[pcorpet]

Fixes #1567.

[coveralls]

Coverage decreased (-0.1%) to 96.176% when pulling 982493d on pcorpet:query-string-extension into b791ba5 on benmosher:master.

[coveralls]

Coverage increased (+0.1%) to 96.367% when pulling e3fa2ce on pcorpet:query-string-extension into 4e8960d on benmosher:master.

[coveralls]

Coverage increased (+0.1%) to 96.367% when pulling e3fa2ce on pcorpet:query-string-extension into 4e8960d on benmosher:master.

[coveralls]

Coverage increased (+0.1%) to 96.367% when pulling e3fa2ce on pcorpet:query-string-extension into 4e8960d on benmosher:master.

[coveralls]

Coverage increased (+0.1%) to 96.367% when pulling e3fa2ce on pcorpet:query-string-extension into 4e8960d on benmosher:master.

[ljharb]

This looks great!