Added another bug future whereby a function with a declared return type but no return statements is not flagged with an error

This is a follow-up to r22103:
* renamed need-missing-return-error --> need-missing-return-error-1
* added need-missing-return-error-2 to show that the error should be reported
  even if the function's return value is not used.


git-svn-id: http://svn.code.sf.net/p/chapel/code/trunk@22104 3a8e244f-b0f2-452b-bcba-4c88e055c3ca