Add Regexp.quote substring spec

Author: eregon

spec/ruby/core/regexp/shared/quote.rb

@@ -12,6 +12,11 @@
     Regexp.send(@method, :symbol).should == 'symbol'
   end
 
+  it "works with substrings" do
+    str = ".+[]()"[1...-1]
+    Regexp.send(@method, str).should == '\+\[\]\('
+  end
+
   it "sets the encoding of the result to US-ASCII if there are only US-ASCII characters present in the input String" do
     str = "abc".force_encoding("euc-jp")
     Regexp.send(@method, str).encoding.should == Encoding::US_ASCII