auto_ptr<char> should not point char array

In CgiEnvironment.cpp and CgiUtils.cpp auto_ptr<char> point char array
allocated by new[]. Such a usage causes undefined behaviour and should
be changed.

Easiest solution:

vector<char> v(size);
foo(&v[0]);

This code is allowed after a recent correct of the standard.

BTW, what do copy construction, assignment and comparison of CgiInput
mean? How should derived classes behave? I can't imagine any
reasonable definition.