Add 64-bit integer converters to our string classes for future work

        * platform/DeprecatedString.cpp:
        (WebCore::DeprecatedString::toInt64):
        (WebCore::DeprecatedString::toUInt64):
        * platform/DeprecatedString.h:

        * platform/PlatformString.h:
        * platform/String.cpp:
        (WebCore::String::toInt64):
        (WebCore::String::toUInt64):

        * platform/StringImpl.cpp:
        (WebCore::StringImpl::toInt64):
        (WebCore::StringImpl::toUInt64):
        * platform/StringImpl.h:



git-svn-id: http://svn.webkit.org/repository/webkit/trunk@24158 268f45cc-cd09-0410-ab3c-d52691b4dbfc