[Bug c++/68284] New: -Wlong-long causes dialect options to be ignored

["rain.backnet at gmail dot com" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68284

            Bug ID: 68284
           Summary: -Wlong-long causes dialect options to be ignored
           Product: gcc
           Version: 5.2.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: rain.backnet at gmail dot com
  Target Milestone: ---

Using the -Wlong-long option seems to cause warnings that ignore the currently
set dialect.  For instance:

    auto main()->int {
      int64_t trillion = 1000000000000ll
    }

Building with:
    g++ -std=c++11 -Wlong-long test.cpp

...produces the incongruous warning:
    warning: use of C++11 long long integer constant [-Wlong-long]


Another example of what appears to be the same bug can be seen at
http://coliru.stacked-crooked.com/a/5d9ffed39a10416e when building in C++11
mode with the warning
    warning: ISO C++ 1998 does not support 'long long' [-Wlong-long]