Fix allusedtext bug, rightmost consulted character incorrect in negative

lookaheads.

ChangeLog

@@ -129,6 +129,10 @@ that is remembered as a minimum length), the whole group's length was
 incorrectly recorded as 65535, leading to incorrect "no match" when start-up 
 optimizations were in force.
 
+29. The "rightmost consulted character" value was not always correct; in 
+particular, if a pattern ended with a negative lookahead, characters that were 
+inspected in that lookahead were not included.
+
 
 Version 10.33 16-April-2019
 ---------------------------

src/pcre2_match.c

@@ -5971,6 +5971,7 @@ in rrc. */
 #define LBL(val) case val: goto L_RM##val;
 
 RETURN_SWITCH:
+if (Feptr > mb->last_used_ptr) mb->last_used_ptr = Feptr;
 if (Frdepth == 0) return rrc;                     /* Exit from the top level */
 F = (heapframe *)((char *)F - Fback_frame);       /* Backtrack */
 mb->cb->callout_flags |= PCRE2_CALLOUT_BACKTRACK; /* Note for callouts */

testdata/testinput15

@@ -231,4 +231,8 @@
 /(*LIMIT_HEAP=21)\[(a)]{60}/expand
     \[a]{60}
 
+/b(?<!ax)(?!cx)/allusedtext
+    abc
+    abcz
+
 # End of testinput15

testdata/testinput2

@@ -4584,7 +4584,7 @@ B)x/alt_verbnames,mark
 
 /abcd/null_context
     abcd\=null_context
-\= Expect error
+\= Expect error - not allowed together
     abcd\=null_context,find_limits
     abcd\=allusedtext,startchar
 

testdata/testoutput15

@@ -525,4 +525,12 @@ No match
     \[a]{60}
 Failed: error -63: heap limit exceeded
 
+/b(?<!ax)(?!cx)/allusedtext
+    abc
+ 0: abc
+    < >
+    abcz
+ 0: abcz
+    < >>
+
 # End of testinput15

testdata/testoutput2

@@ -14803,7 +14803,7 @@ No match
 /abcd/null_context
     abcd\=null_context
  0: abcd
-\= Expect error
+\= Expect error - not allowed together
     abcd\=null_context,find_limits
 ** Not allowed together: find_limits null_context
     abcd\=allusedtext,startchar