Small update to pcre2compat description of braced quantifiers

Author: NWilson

doc/pcre2compat.3

@@ -34,7 +34,11 @@ any kind of quantifier on non-lookaround assertions.
 .P
 4. If a braced quantifier such as {1,2} appears where there is nothing to
 repeat (for example, at the start of a branch), PCRE2 raises an error whereas
-Perl treats the quantifier characters as literal.
+Perl treats the quantifier characters as literal. When a braced quantifier
+(...){min,max} has min > max, Perl treats it as an item which fails to match
+any portion of the subject (as no number of repetitions can meet the
+condition), and additionally issues a warning when in warning mode. PCRE2 has
+no warning features, so it gives an error in this case.
 .P
 5. Capture groups that occur inside negative lookaround assertions are counted,
 but their entries in the offsets vector are set only when a negative assertion