This is already in a previous version.
General maintenance of int/size_t vars, and new logic to search for keys.

- use less size_t, use more int. Most of the size_t-s were unnecessary.
- use const variables for function parameters, where possible.
- use unsigned variables for function parameters and elsewhere, where it is justified.
- remove unnecessary (long) castings. I think lint messed with these a long time ago...
- use xmlStrlen() with xmlChar-s, and don't use needless type casting.
- fine-tune checks for spice, explicitly check if it is greater than 0.
- find_key() logic rewrite. eg.: don't start the index var. from -1 ... .
- when dealing with value lines, precalculate their lengths, and don't call (xml)strlen every time in a loop.
Add getnum and 'c' command tests for negative and large numbers.