Use cat19 for 1.1 branch that will fade away soon

This fixes #247 without introducing a dependency on the new
catWithCodeRange in JRuby 9.4. It does depend on a now-deprecated
method cat19 that will go away in the next year or so.

src/main/java/org/jruby/rack/RackInput.java

@@ -27,6 +27,7 @@
 import org.jruby.runtime.ThreadContext;
 import org.jruby.runtime.builtin.IRubyObject;
 import org.jruby.util.ByteList;
+import org.jruby.util.StringSupport;
 
 /**
  * Native (Java) implementation of a Rack input.
@@ -147,7 +148,7 @@ public IRubyObject read(ThreadContext context, IRubyObject[] args) {
             if (bytes != null) {
                 if (string != null) {
                     string.clear();
-                    string.cat(bytes);
+                    string.cat19(new ByteList(bytes, false), StringSupport.CR_UNKNOWN);
                     return string;
                 }
                 return getRuntime().newString(new ByteList(bytes));