[Bug target/67353] New: [avr] Option-ize Warning "appears to be a misspelled signal / interrupt handler"

[gjl at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67353

            Bug ID: 67353
           Summary: [avr] Option-ize Warning "appears to be a misspelled
                    signal / interrupt handler"
           Product: gcc
           Version: 5.2.0
            Status: UNCONFIRMED
          Keywords: diagnostic
          Severity: normal
          Priority: P3
         Component: target
          Assignee: gjl at gcc dot gnu.org
          Reporter: gjl at gcc dot gnu.org
  Target Milestone: ---
            Target: avr

Add -W flag to control the mentioned warning or turn it into an error.