converting to/from char[]/string

[mark]

I changed int to size_t and used const(char[]) etc. as suggested.
It ran but crashed. Each crash was a range violation, so for each 
one I put in a guard so instead of

if ( ... m_b[m_k])

I used

if (m_k < m_b.length && ... m_b[m_k)

I did this kind of fix in three places.

The result is that it does some but not all the stemming!

Anyway, I'll compare it with the Python version and see if I can 
spot the problem(s).

Thanks.