Slightly reworked lexer to for a few directives:

'opt' and several other directives ('printt', 'fail' etc.) no longer causes a syntax error when unquoted.
'include', 'incdir' and 'incbin' and 'output' with '<pathname>' quotes no longer cause syntax error.

src/test/resources/parser/directives/include_file_unquoted.txt

@@ -6,7 +6,6 @@ Assembly File: a.asm
         PsiElement(M68kTokenType.COLON)(':')
       PsiElement(M68kTokenType.OTHER_DIRECTIVE)('incbin')
       PsiWhiteSpace(' ')
-      M68kRefExprImpl(REF_EXPR)
-        M68kSymbolReferenceImpl(SYMBOL_REFERENCE)
-          PsiElement(M68kTokenType.SYMBOL)('Convertedassets\scroller_howto.raw.BPL')
+      M68kLiteralExprImpl(LITERAL_EXPR)
+        PsiElement(M68kTokenType.STRINGLIT)('Convertedassets\scroller_howto.raw.BPL')
   PsiElement(M68kTokenType.EOL)('\n')

src/test/resources/parser/directives/kalms_include_file_special_quote.txt

@@ -0,0 +1,8 @@
+Assembly File: a.asm
+  PsiWhiteSpace(' ')
+  M68kStatementImpl(STATEMENT)
+    M68kPreprocessorDirectiveImpl(PREPROCESSOR_DIRECTIVE)
+      PsiElement(M68kTokenType.OTHER_DIRECTIVE)('include')
+      PsiWhiteSpace('\t')
+      M68kLiteralExprImpl(LITERAL_EXPR)
+        PsiElement(M68kTokenType.STRINGLIT)('<Engine/A500/System/Copper.i>')

src/test/resources/parser/directives/opt_directive.txt

@@ -0,0 +1,11 @@
+Assembly File: a.asm
+  PsiWhiteSpace(' ')
+  M68kStatementImpl(STATEMENT)
+    M68kPreprocessorDirectiveImpl(PREPROCESSOR_DIRECTIVE)
+      PsiElement(M68kTokenType.OTHER_DIRECTIVE)('opt')
+      PsiWhiteSpace(' ')
+      M68kLiteralExprImpl(LITERAL_EXPR)
+        PsiElement(M68kTokenType.STRINGLIT)('o+')
+      PsiElement(M68kTokenType.SEPARATOR)(',')
+      M68kLiteralExprImpl(LITERAL_EXPR)
+        PsiElement(M68kTokenType.STRINGLIT)('w-')