encoding/wkt: wkt decoding case and space insensitive

[otan]

Trying to replace my WKT decoding from cgo-ing with GEOS with the go-geom one here.

Unfortunately, it doesn't work for a couple of cases, e.g.

• POINT(1.0 1.0) should work (no space between POINT and ()
• point (1.0 1.0) should work (case insensitive POINT)
• POINTZ (1.0 1.0) should work (Z dimension / layout does not need a space afterwards)

Wondering if it's worth using a grammar file (https://godoc.org/golang.org/x/tools/cmd/goyacc) to do this instead.

I can work on this at a later date, but flagging as an issue for now. (It's not straightforward based on the way things are tokenised right now in the wkt decoder)

[twpayne]

Thanks for flagging this. I agree that using a parser generator will give a more robust parser than the existing code. Feel free to rework the WKT parser completely if you want.