[GTK] REGRESSION(r147499): HTTP auth dialog doesn't remember passwords anymore
https://bugs.webkit.org/show_bug.cgi?id=114613

Reviewed by Carlos Garcia Campos.

* Source/autotools/SetupAutoconfHeader.m4: Correct definition of ENABLE_CREDENTIAL_STORAGE
so that the ENABLE(CREDENTIAL_STORAGE) macro work properly.

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@148445 268f45cc-cd09-0410-ab3c-d52691b4dbfc