Preliminary implementation of strtol()

Created by: Arcterus

I believe there are still bugs and places where I do not conform fully to the standards, but most of the code is done. What is present can easily be used as the basis for strtoul() as well (basically just remove the checks for +/- and use the overflow value returned by convert_integer() instead of checking for overflow after casting to a signed long).

I added octal support to printf() to aid in testing.