changed some variable types

Sorry, this was really pedantic - I was just looking at the valgrind output and spotted some of these (well only the delete one) and went though some of the gcc errors about unsigned ints. I'm not sure if you were using the unsigned int rule or just using them normally.

Also there are a significant number of warnings/errors highligted by valgrind regarding uninitialized values in:
```c++
phi0_power::dTau(double, double) (Helmholtz.h line 711), and
phi0_power::base(double, double) (Helmholtz.h line 702).
```

Anyway, feel free to ignore this patch! :+1: