Correct some comments

nPCOffset no longer exists, and the lexer only
returns T_NEWLINE for EOF in raw mode.

include/asm/rpn.h

@@ -27,9 +27,6 @@ struct Expression {
 	uint32_t nRPNPatchSize; // Size the expression will take in the obj file
 };
 
-/* FIXME: Should be defined in `parser.h`, but impossible with POSIX Yacc */
-extern int32_t nPCOffset;
-
 /*
  * Determines if an expression is known at assembly time
  */