Remove dead code for handling quantifier after OP_FAIL

Fixes #541

Author: NWilson

src/pcre2_compile.c

@@ -7110,15 +7110,6 @@ for (;; pptr++)
         }
       break;
 
-      /* The ways in which OP_FAIL can be generated, that is by (*FAIL) or
-      (?!), disallow a quantifier at parse time. We ought to be able to ignore this. */
-
-      case OP_FAIL:
-      /* TODO: [EC] https://github.com/PCRE2Project/pcre2/issues/541
-      Should this be removed, now that '[]' has been changed so it doesn't produce OP_FAIL? */
-      PCRE2_UNREACHABLE();
-      goto END_REPEAT;
-
       /* Prior to 10.30, repeated recursions were wrapped in OP_ONCE brackets
       because pcre2_match() could not handle backtracking into recursively
       called groups. Now that this backtracking is available, we no longer need
@@ -7527,9 +7518,9 @@ for (;; pptr++)
       here because it just makes it horribly messy. */
 
       default:
-      if (op_previous >= OP_EODN)   /* Not a character type - internal error */
+      if (op_previous >= OP_EODN || op_previous <= OP_WORD_BOUNDARY)
         {
-        *errorcodeptr = ERR10;
+        *errorcodeptr = ERR10;  /* Not a character type - internal error */
         return 0;
         }
       else