qemu-hppa floating point POWER function is incorrect
Description of problem:
The floating point power function produces incorrect values, and possibly stack misshapes as well.
Steps to reproduce:
1. $ hppa1.1-unknown-linux-gnu-gcc pow.c -o pow -lm -static
2. $ qemu-hppa pow
3. the expected result is 10.0 ^ 6.0 = 6000000.0, instead of 403.45
Additional information:
Example C source to reproduce, pow.c:
```
#include <stdio.h>
#include <math.h>
int main()
{
    double base, expo, res;
    base=10.0;
    expo=6.0;
    // res sould be 1e+6
    res = pow(base, expo);
    printf("%.1lf^%.1lf = %.2lf\n", base, expo, res);
    return 0;
}
```