This VMOD implements basic variable in VCL. Well. It's more of an
association list with support for strings, ints and reals.

There are methods to get and set each type.

Global variables have a lifespan that extends across requests and
VCLs, for as long as the vmod is loaded. Non-globals are local to a
single request.

Prototype, most should be self-explaining:

Function VOID set(STRING, STRING)
Function STRING get(STRING)

Function VOID global_set(STRING, STRING)
Function STRING global_get(STRING)

Function VOID set_int(STRING, INT)
Function INT get_int(STRING)

Function VOID set_string(STRING, STRING)
Function STRING get_string(STRING)

Function VOID set_real(STRING, REAL)
Function REAL get_real(STRING)

Function VOID set_duration(STRING, DURATION)
Function DURATION get_duration(STRING)

Function VOID clear()

clear() clears the whole non-global variable space.