Irix 6.2:
- math.h: defines extern long double hypotl( long double );  i.e., only
          one argument.  They've fixed this in 6.3.

DES OSF 3.2 & 4.0:
- libm define sincos, sincosf, and sincosl but there are no prototypes and
  especially the return type is nowhere defined.  The functions are
  documented in the man pages, though.