Fix (?R- not being correctly diagnosed.

ChangeLog

@@ -69,6 +69,9 @@ the LLVM fuzzer.
 18. A conditional group with only one branch has an implicit empty alternative 
 branch and must therefore be treated as potentially matching an empty string.
 
+19. If (?R was followed by - or + incorrect behaviour happened instead of a
+diagnostic. This bug was discovered by Karl Skomski with the LLVM fuzzer.
+
 
 Version 10.20 30-June-2015
 --------------------------

src/pcre2_compile.c

@@ -6394,9 +6394,14 @@ for (;; ptr++)
 
 
         /* ------------------------------------------------------------ */
-        case CHAR_R:              /* Recursion */
-        ptr++;                    /* Same as (?0)      */
-        /* Fall through */
+        case CHAR_R:              /* Recursion, same as (?0) */
+        recno = 0;
+        if (*(++ptr) != CHAR_RIGHT_PARENTHESIS)
+          {
+          *errorcodeptr = ERR29;
+          goto FAILED;
+          }
+        goto HANDLE_RECURSION;
 
 
         /* ------------------------------------------------------------ */

testdata/testinput2

@@ -4354,4 +4354,6 @@ a random value. /Ix
 
 /()(?(R)0)*+/B
 
+/(?R-:(?</
+
 # End of testinput2 

testdata/testoutput2

@@ -14553,4 +14553,7 @@ Failed: error 106 at offset 353: missing terminating ] for character class
         End
 ------------------------------------------------------------------
 
+/(?R-:(?</
+Failed: error 129 at offset 3: (?R or (?[+-]digits must be followed by )
+
 # End of testinput2