The variable maxCodeLen is the limit on how long the returned
Caverphone code should be. The default is 6, unless modified
is set to TRUE, then the default is 10.
The variable modified directs caverphone to use the
Caverphone2 method, instead of the original.
The caverphone algorithm is only defined for inputs over the
standard English alphabet, i.e., "A-Z.". Non-alphabetical
characters are removed from the string in a locale-dependent fashion.
This strips spaces, hyphens, and numbers. Other letters, such as
"<U+00DC>," may be permissible in the current locale but are unknown to
caverphone. For inputs outside of its known range, the output is
undefined and NA is returned and a warning this thrown.
If clean is FALSE, caverphone attempts to process the
strings. The default is TRUE.