OpenSCAD parser issue

I've come across an openscad lib which seems to find bugs in the parser.

https://www.dkprojects.net/openscad-threads/threads.scad

```
$ extopenscad lib/threads.scad
Loading File.
Processing File.
(line 100, column 8):
unexpected "m"
expecting "//", "/*" or "("
```

The line(s) referenced:
```
module metric_thread (diameter=8, pitch=1, length=1, internal=false, n_starts=1,
thread_size=-1, groove=false, square=false, rectangle=0,
angle=30, taper=0, leadin=0, leadfac=1.0, test=false)
```

This same file is processed fine via `openscad`