Implement -Wstrict-typing

[yutaro-sakamoto]

This pull request adds -Wstrict-typing which warns type mismatches strictly.
The following is an example of this option.

prog.cbl

       IDENTIFICATION DIVISION.
       PROGRAM-ID. prog.
       DATA DIVISION.
       WORKING-STORAGE SECTION.
       01 X PIC X(5).
       01 X-EDIT PIC X(3),X(2).
       01 N PIC N(5).
       01 NUM PIC 9(5).
       01 NUM-EDIT PIC 9(3),9(2).
       PROCEDURE DIVISION.
       MAIN SECTION.
         MOVE 12345 TO X.
         MOVE 12345 TO X-EDIT.
         MOVE 12345 TO N.
         MOVE "12345" TO NUM.
         MOVE "12345" TO NUM-EDIT.

> cobj -Wstrict-typing prog.cbl
prog.cbl:12: Warning: Alphanumeric value is expected
prog.cbl:5: Warning: 'X' defined here as PIC X(5)
prog.cbl:13: Warning: Alphanumeric value is expected
prog.cbl:6: Warning: 'X-EDIT' defined here as PIC X(3),X(2)
prog.cbl:14: Warning: National value is expected
prog.cbl:7: Warning: 'N' defined here as PIC N(5)
prog.cbl:15: Warning: Numeric value is expected
prog.cbl:8: Warning: 'NUM' defined here as PIC 9(5)
prog.cbl:16: Warning: Numeric value is expected
prog.cbl:9: Warning: 'NUM-EDIT' defined here as PIC 9(3),9(2)