Patch for COMPLEX support

[Weiwen Liu]

I am sending a patch to fix the support for complex arguments.  I have
tested this patch on alphaev56-dec-osf4.0 and sparc-sun-solaris2.  On
alpha, this patch introduces no regression from 'make check-gcc' and
'make check-g++'.

I have separated the patch into two parts which are contained in
separate emails.
 
I would appreciate if this patch can be tested on other platforms.

The test case I use is:

#ifndef F
#define F int
#endif

typedef __complex__ F FC;

FC f1(int odd, FC a, FC b, FC c, FC d)
{
  return a + b + c + d;
}

FC f2a(F a, F b, F c, F d, F e, F f, F g, F h)
{
  return (a + c + e + g) + 1i * (b + d + f + h);
}

FC f2b(FC a, FC b, FC c, FC d)
{
  return a + b + c + d;
}

int main()
{
    FC a, b, c, d, e;
    a = -1 + 2i;
    b = -3+4i;
    c = -5+6i;
    d = -7+8i;

    e=f2b(a,b,c,d);
    if (e != -16+20i)
        abort ();
    e=f2a(-1,2,-3,4,-5,6,-7,8);
    if (e != -16+20i)
    abort ();
    e = f1(1,a,b,c,d);
    if (e != -16+20i)
    abort ();
    return 0;
}

I have tested with F=(char, short, int, long, float, double) and with
no-optimization, -O1, -O2, -O3.