OpenSCAD type detector

Description

This is a small library to detect the types of OpenSCAD variables/expressions. Publicly exposed functions are: isVector(x), isBoolean(x), isFloat(x), isDefiniteFloat(x) (float, but not NaN or infinity), isRange(x), isString(x) and typeOf(x). The last of these returns a string describing the type: vector, boolean, float, range, string, undef, unknown. Googling showed other solutions to the type detection problem, but I worked to make my solution as efficient as possible. Update: More speed. In particular, I now avoid concat() and I also noticed that len() runs in O(1) time when applied to a vector but O(n) when applied to a string of length n, so I now avoid applying len() to strings, and as a result all the functions should now run in O(1) time. Update: May 8, 2017: Optimized typeOf() by removing function calls and duplication of code between tests.