Constants in EXTNAME are incorrectly treated as literal file names

[FraGag]

According to the documentation for EXTNAME:

• In a free-form definition, the file-name and format-name parameters must be character literals or named constants representing character literals. If a parameter is a named constant, the constant must be defined prior to the definition statement.
• In a fixed-form definition, the file-name and format-name parameters can be either names or character literals.

Source Orbit doesn't handle this distinction correctly; it uses the "fixed-form definition" semantics even in free-form definitions.

Steps to reproduce

1. git clone https://github.com/IBM/ibmi-company_system.git
2. git checkout c94ca30387de18f0d28af5f5669849c1773cfd76
3. so -- This should output nothing.
4. Apply the following patch:

diff --git a/qrpglesrc/depts.pgm.sqlrpgle b/qrpglesrc/depts.pgm.sqlrpgle
index 37b5f5c..7deb695 100755
--- a/qrpglesrc/depts.pgm.sqlrpgle
+++ b/qrpglesrc/depts.pgm.sqlrpgle
@@ -54,7 +54,8 @@
       *
           Dcl-S Index Int(5);
 
-          Dcl-Ds Department ExtName('DEPARTMENT') Alias Qualified;
+          Dcl-S C_Department 'DEPARTMENT';
+          Dcl-Ds Department ExtName(C_Department) Alias Qualified;
           End-Ds;
 
           

5. so -- This now outputs:

qrpglesrc/depts.pgm.sqlrpgle:57 - No object found for reference 'C_DEPARTMENT'

It's interpreting C_DEPARTMENT as the file name, instead of as a constant name that needs to be looked up and resolved, yielding DEPARTMENT as the file name.