intprops and warnings

[Simon Josefsson]

Libtasn1 recently started to use the intprops module, however it
generates warnings:

make[3]: Entering directory `/home/jas/src/libtasn1/lib'
  CC     decoding.lo
decoding.c: In function 'asn1_get_length_der':
decoding.c:88:15: error: comparison of unsigned expression < 0 is always false 
[-Werror=type-limits]
decoding.c:88:15: error: comparison of unsigned expression < 0 is always false 
[-Werror=type-limits]
decoding.c:88:15: error: comparison of unsigned expression < 0 is always false 
[-Werror=type-limits]
decoding.c:88:15: error: comparison of unsigned expression < 0 is always false 
[-Werror=type-limits]
decoding.c:88:15: error: comparison of unsigned expression < 0 is always false 
[-Werror=type-limits]
decoding.c:88:15: error: comparison of unsigned expression < 0 is always false 
[-Werror=type-limits]
decoding.c:88:15: error: comparison of unsigned expression < 0 is always false 
[-Werror=type-limits]
decoding.c:88:15: error: comparison of unsigned expression < 0 is always false 
[-Werror=type-limits]

The code in question is:

    62  long
    63  asn1_get_length_der (const unsigned char *der, int der_len, int *len)
    64  {
    65    unsigned int ans;
...
    86            while (punt <= k && punt < der_len)
    87              {
    88                if (INT_MULTIPLY_OVERFLOW (ans, 256))
    89                  return -2;

Is there a problem in the libtasn1 code?

Is this an unavoidable consequences of using the intprops module?  Then
I'll just add -Wno-error=type-limits, although that seems unfortunate to
need that since we didn't before.

/Simon