Preprocess the target macro based on the macro parameter list.

[skyfish4tb]

'' __FB_ARG_LISTEXPAND__(MacroName, MacroArgCount , args...)
'' Retuns empty string on invalid index, rather than compile error.
'' MacroName     : the name of the macro used for extension calls.
'' MacroArgCount : the number of parameters for the MacroName macro.Expand the parameter list Args according to the MacroArgCount value.
''                 1, MacroArgCount>0, pass MacroArgCount parameters each time;
'                  2, MacroArgCount=0, pass all parameters;
''                 3, MacroArgCount<0, for each parameter passed, the previous MacroArgCount parameters are automatically removed on the next pass.
'' args...       : argument list(The number of Args parameters passed may not be an integer multiple of MacroArgCount.)

#macro m( arg... )
    #print "   "##arg
#endmacro

#print "1. MacroArgCount=0:"
__FB_ARG_LISTEXPAND__( m, 0, Hello1, Hello2, Hello3, Hello4)
#print "2. MacroArgCount>0:"
__FB_ARG_LISTEXPAND__( m, 1, Hello1, Hello2, Hello3, Hello4)
#print "3. MacroArgCount<0:"
__FB_ARG_LISTEXPAND__( m, -1, Hello1, Hello2, Hello3, Hello4)

/' Compiler output:
   1. MacroArgCount=0:
      Hello1, Hello2, Hello3, Hello4
   2. MacroArgCount>0:
      Hello1
      Hello2
      Hello3
      Hello4
   3. MacroArgCount<0:
      Hello1, Hello2, Hello3, Hello4
      Hello2, Hello3, Hello4
      Hello3, Hello4
      Hello4
'/

[jayrm]

This appears to be an improvement over the commit in #312 __FB_ARG_LOOPEXPAND__

While it does seem of specific use, this new version generally looks OK to add.

It needs a couple of corrections:

1. sizeof(wstring) may vary on different hosts so ushort ptr can't be assumed.
2. NEWLINE should only be added if the macro expansion results in multiple lines, otherwise it throws off the internal line number counter
3. tests in the test-suite

I will post fixes soon.