[Bug c/65213] New: Extend -Wmissing-declarations to variables

[eugene.zelenko at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65213

            Bug ID: 65213
           Summary: Extend -Wmissing-declarations to variables
           Product: gcc
           Version: 5.0
            Status: UNCONFIRMED
          Severity: enhancement
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: eugene.zelenko at gmail dot com

Will be good idea to -Wmissing-declarations to variables. Global variable
should have extern declaration in header file, otherwise variable should be
static.

Clang detect such situations with -Wmissing-variable-declarations.

Same should be done for C++.