parse-datetime.y reports integer overflow when compiled with gcc 5.5.0

[Sergey Poznyakoff]

Hello,

With recent gnulib (v0.1-4336-gbdae9a5), attempting to compile
parse-datetime.c fails with:

$ make -k parse-datetime.o V=1
gcc -DHAVE_CONFIG_H -I. -I..     -Wall -ggdb -MT parse-datetime.o -MD -MP -MF 
.deps/parse-datetime.Tpo -c -o parse-datetime.o parse-datetime.c
In file included from parse-datetime.y:39:0:
parse-datetime.y: In function 'to_tm_year':
intprops.h:578:17: warning: integer overflow in expression [-Woverflow]
       || (tmax) + (b) < (a)))
                 ^
intprops.h:524:4: note: in expansion of macro '_GL_INT_SUBTRACT_RANGE_OVERFLOW'
   (overflow (a, b, tmin, tmax) \
    ^
intprops.h:491:10: note: in expansion of macro '_GL_INT_OP_CALC'
        ? _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned int, \
          ^
intprops.h:389:4: note: in expansion of macro '_GL_INT_OP_WRAPV'
    _GL_INT_OP_WRAPV (a, b, r, -, _GL_INT_SUBTRACT_RANGE_OVERFLOW)
    ^
parse-datetime.y:1274:9: note: in expansion of macro 'INT_SUBTRACT_WRAPV'
       : INT_SUBTRACT_WRAPV (year, TM_YEAR_BASE, tm_year))
         ^
parse-datetime.y: In function 'yylex':
intprops.h:578:17: warning: integer overflow in expression [-Woverflow]
       || (tmax) + (b) < (a)))
                 ^
intprops.h:524:4: note: in expansion of macro '_GL_INT_SUBTRACT_RANGE_OVERFLOW'
   (overflow (a, b, tmin, tmax) \
    ^
intprops.h:500:11: note: in expansion of macro '_GL_INT_OP_CALC'
         ? _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned long int, \
           ^
intprops.h:495:7: note: in expansion of macro '_GL_INT_OP_WRAPV_LONGISH'
     : _GL_INT_OP_WRAPV_LONGISH(a, b, r, op, overflow))
       ^
intprops.h:389:4: note: in expansion of macro '_GL_INT_OP_WRAPV'
    _GL_INT_OP_WRAPV (a, b, r, -, _GL_INT_SUBTRACT_RANGE_OVERFLOW)
    ^
parse-datetime.y:1469:23: note: in expansion of macro 'INT_SUBTRACT_WRAPV'
                   if (INT_SUBTRACT_WRAPV (s, 1, &s))
                       ^

Bisecting shows that the bug was introduced by commit 
55168f5fa7b3b95fbaa2be525b15f6ecd5500c02
                       
Regards,
Sergey