Fix erlang makefile so that regress and clean work correctly
Fix some bad erling code that made it into the last commit
Make erlang library work on R15+

Previously, it used the regexp library, which was removed in R15.
This makes the minimum version to run R13, since the new re module
was introduced then.
Fix example code in README
Add erlang test suite using test-files
Make license file naming consistent, update copyright years