Add regexp regression tests

- Bug 757711: heap-buffer-overflow in xmlFAParsePosCharGroup
  <https://bugzilla.gnome.org/show_bug.cgi?id=757711>
- Bug 783015 - Integer-overflow in xmlFAParseQuantExact
  <https://bugzilla.gnome.org/show_bug.cgi?id=783015>

(Regexptests): Add support for checking stderr output when
running regexp tests.  This makes it possible to check in test
cases that fail and not see false-positive error output when
running the tests.  Unlike other libxml2 test suites, if there
is no stderr output, no *.err file needs to be created.

Makefile.am

@@ -907,14 +907,16 @@ Regexptests: testRegexp$(EXEEXT)
 	  if [ ! -d $$i ] ; then \
 	  if [ ! -f $(srcdir)/result/regexp/$$name ] ; then \
 	      echo New test file $$name ; \
-	      $(CHECKER) $(top_builddir)/testRegexp -i $$i > $(srcdir)/result/regexp/$$name; \
+	      $(CHECKER) $(top_builddir)/testRegexp -i $$i > $(srcdir)/result/regexp/$$name 2> $(srcdir)/result/regexp/$$name.err ; \
+	      if [ ! -s "$(srcdir)/result/regexp/$$name.err" ] ; then rm $(srcdir)/result/regexp/$$name.err; fi ; \
 	      grep "MORY ALLO" .memdump  | grep -v "MEMORY ALLOCATED : 0";\
 	  else \
-	      log=`$(CHECKER) $(top_builddir)/testRegexp -i $$i 2>&1 > result.$$name ; \
+	      log=`$(CHECKER) $(top_builddir)/testRegexp -i $$i > result.$$name 2> error.$$name ; \
 	      grep "MORY ALLO" .memdump  | grep -v "MEMORY ALLOCATED : 0";\
-	      diff $(srcdir)/result/regexp/$$name result.$$name` ; \
-	      if [ -n "$$log" ] ; then echo $$name result ; echo "$$log" ; fi ; \
-	      rm result.$$name ; \
+	      diff $(srcdir)/result/regexp/$$name result.$$name ; \
+	      if [ -s "$(srcdir)/result/regexp/$$name.err" -o -s "error.$$name" ] ; then diff $(srcdir)/result/regexp/$$name.err error.$$name ; fi` ; \
+	      if [ -n "$$log" ] ; then echo $$name result ; echo $$log ; fi ; \
+	      rm result.$$name error.$$name ; \
 	  fi ; fi ; done)
 
 # Disabled for now

result/regexp/bug757711

@@ -0,0 +1,2 @@
+Regexp: [;^((-
+   failed to compile

result/regexp/bug757711.err

@@ -0,0 +1,2 @@
+regexp error : failed to compile: Expecting the end of a char range
+regexp error : failed to compile: xmlFAParseCharClass: ']' expected

result/regexp/bug783015

@@ -0,0 +1,4 @@
+Regexp: .{2147483647}
+input: Fail
+Regexp: .{2147483648}
+   failed to compile

result/regexp/bug783015.err

@@ -0,0 +1 @@
+regexp error : failed to compile: Improper quantifier

test/regexp/bug757711

@@ -0,0 +1 @@
+=>[;^((-

test/regexp/bug783015

@@ -0,0 +1,4 @@
+# This assumes 32-bit ints.
+=>.{2147483647}
+input
+=>.{2147483648}