Use original program when constructing ProgramStatement.

This means that ProgramStatements now refer to the file they actually
occur in, like is the case for the original SourceLine.  This is used
for various diagnostics messages.

Fixes #160.

src/rars/assembler/Assembler.java

@@ -488,7 +488,7 @@ private ArrayList<ProgramStatement> parseLine(TokenList tokenList, String source
                         "Extended (pseudo) instruction or format not permitted.  See Settings."));
             }
             if (OperandFormat.tokenOperandMatch(tokens, inst, errors)) {
-                programStatement = new ProgramStatement(this.fileCurrentlyBeingAssembled, source,
+                programStatement = new ProgramStatement(token.getOriginalProgram(), source,
                         tokenList, tokens, inst, textAddress.get(), sourceLineNumber);
                 // instruction length is 4 for all basic instruction, varies for extended instruction
                 // Modified to permit use of compact expansion if address fits

src/rars/assembler/SourceLine.java

@@ -97,4 +97,4 @@ public int getLineNumber() {
     public RISCVprogram getRISCVprogram() {
         return program;
     }
-}
+}