#444 intrinsic functions: missing checks for argument type used

[Simon Sobisch]

We currently check only the number of arguments but not their type. See "Summary of functions -> Table of functions" in the 2002+ standard (15.6/Table23 in ISO/IEC 1989:20xx FCD 1.0 E) and/or MF docs: Definitions of Functions.

For example it is not allowed to specify a numeric expression in FUNCTION NUMVAL which should only take alphanumeric/national items/constants/literals as arguments.