Fix for #98: deal with variable-free for [...] loops.

This small fix (thanks to Kevin Zatloukal) uses a generated variable
for a variable-free for loop; and it adds a small test for that case.
Merge pull request #116 from PencilCode/issue98

Fix for #98: deal with variable-free for [...] loops.
Build with previous bugfix
version bump to v1.7.1-b
more compile with new version #