Added tests for stdlib subroutine `strlen`.

[vvhitespace] / stdlib_tests / 4001_strlen.pvvs

A"Hello World"
SSSTSSSSSN      | PUSH 32 (address)
SSSTSTTN        | PUSH 11 (count)
NSTTTTTTN       | JSR > 11111 (spew)

SSSTSSSSSN      | PUSH 32 (address)
NSTTSSSSSN      | JSR > 100000 (strlen)
NSTTSSTN        | JSR > 1001 (print number from stack)

NNN             | DIE

#include <stdio.pvvs>
#include <heap.pvvs>
#include <string.pvvs>