Regex: Fix lookaround use in moon.kak

(?=[A-Z]\w*) is strictly the same as (?=[A-Z]) as \w* will always
at least match an empty string.

src/regex_impl.cc

@@ -1067,13 +1067,13 @@ auto test_regex = UnitTest{[]{
     }
 
     {
-        TestVM<> vm{R"((?!foo)...)"};
+        TestVM<> vm{R"((?!f[oa]o)...)"};
         kak_assert(not vm.exec("foo"));
         kak_assert(vm.exec("qux"));
     }
 
     {
-        TestVM<> vm{R"(...(?<=foo))"};
+        TestVM<> vm{R"(...(?<=f.o))"};
         kak_assert(vm.exec("foo"));
         kak_assert(not vm.exec("qux"));
     }

src/regex_impl.hh

@@ -388,8 +388,11 @@ private:
             auto cp = (look_direction == MatchDirection::Forward ? *pos : *(pos-1)), ref = *it;
             if (ref == 0xF000)
             {} // any character matches
-            else if (ref > 0xF0000 and ref <= 0xFFFFD and not m_program.matchers[ref - 0xF0001](cp))
-                return false;
+            else if (ref > 0xF0000 and ref <= 0xFFFFD)
+            {
+                if (not m_program.matchers[ref - 0xF0001](cp))
+                    return false;
+            }
             else if (ref != cp)
                 return false;