Add longer flags

It is now possible to use longer flags instead of the short one-letter ones.

test/init.nim

@@ -10,6 +10,11 @@ suite "Test NRE initialization":
     expect(SyntaxError):  # ValueError would be bad
       discard re("[0-9]+",
         "89AEfimNsUWXxY<any><anycrlf><cr><crlf><lf><bsr_anycrlf><bsr_unicode><js><no_study>")
+    expect(SyntaxError):
+      discard re("[0-9]+",
+        "<utf8><no_utf8><anchored><dollar_endonly><firstline>" &
+        "<case_insensitive><multiline><no_auto_capture><dotall><ungreedy>" &
+        "<ucp><extra><extended><no_start_optimize>")
 
   test "incorrect options":
     expect(KeyError): discard re("[0-9]+", "a")