Add CCSID keyword to declared constants

Situation

When we run a program in environments with different CCSID's and that program is using literals containing characters with different code points in different CCSID's (like square brackets '[' and ']' in CCSID 1140 and 1148) then ctl-opt CCSID(*EXACT) comes in handy. Thank you for providing that!

Problem description

The downside of using that control option is that functions like %scan, %scanr and %scanrpl (and probably others) become picky when the first parameter is a literal string. I ran into problems concatenating x'0D0A' (CRLF) as well but will focus on %scan in the examples provided below. 

Normally this works well (with default CCSID(*NOEXACT) ) 

dcl-s myText char(10);
dcl-s position int(5);
position = %scan('A': myText);

With CCSID(*EXACT) this fails compiling with "RNF0353 The first and second parameters of %SCAN or %SCANR are not of the same type."                                               

ctl-opt ccsid(*exact);

dcl-s myText char(10);
dcl-s position int(5);
position = %scan('A': myText) 

When you use this constant value 'A' multiple times, it's always better to create a constant, so let's do that. However, this code still fails compilation with RNF0353.

ctl-opt ccsid(*exact);

dcl-s myText char(10);
dcl-s position int(5);
dcl-c constA 'A';

position = %scan(constA: myText) 

Only when 'A' is defined as an initial value for a variable it will compile

ctl-opt ccsid(*exact);

dcl-s myText char(10);
dcl-s position int(5);
dcl-s varA varchar(1) inz('A');

position = %scan(varA: myText) 

position = %scan(%char('A'): myText) 

Also an explicit cast to a character value works, provided that the CCSID's match

ctl-opt ccsid(*exact) ccsid(*char: 1148);

dcl-s myText1140 char(10) CCSID(1140);
dcl-s myText1148 char(10); // implicitly ccsid 1148
dcl-s position int(5);

// compiles
position = %scan(%char('A'): myText1148) 

// compiles
position = %scan(%char('A': 1140): myText1140) 

// fails
position = %scan(%char('A'): myText1140) 

Suggested solution

What I would like to see is that the functions like %scan can handle a constant as parameter, even with CCSID(*EXACT). I think that this requires the constant to be defined with a CCSID as well because variant characters like '[' and ']' need to be defined with a CCSID in order to know the hex value associated with them. 

ctl-opt ccsid(*exact);

// variant constant characters with different hex representations
dcl-c con1 '[' ccsid(1140);
dcl-c con2 '[' ccsid(1148);
dcl-c con3 '[' ccsid(*utf8);

This would be necessary for dcl-enum as well.