Wide character string conversion subroutines

The following multicultural support subroutines convert wide character strings to double, long, and unsigned long integers:

wcstod

Converts a wide character string to a double-precision floating point.

wcstol

Converts a wide character string to a signed long integer.

wcstoul

Converts a wide character string to an unsigned long integer.

Before calling the wcstod, wcstoul, or wcstol subroutine, the errno global variable must be set to 0. Any error that occurs as a result of calling these subroutines can then be handled correctly.