Fixes to rfc7230:

fix #1435, fix #1438

* Example and test can be built on msvc v141 15.9.6
  using /std:c++17 and BOOST_BEAST_USE_STD_STRING_VIEW.

* changed string_view.to_string() to std:string(string_view),
  awaiting availability of Library Fundamentals TS here.

* Reactivated relevant tests to param_list. #ifdef 0 test
  exhibited same assertion failed error in debug mode.
  Now fixed in DEBUG on msvc v141 15.9.6 with
  BOOST_BEAST_USE_STD_STRING_VIEW and /std:c++17.

* Looked up http paramters (transfer-encoding, etc.)
  and changed tests as well as fixing comment to
  match specs.

test/beast/http/rfc7230.cpp

@@ -88,6 +88,9 @@ public:
         cq("\t; \t xyz=1 ; ijk=\"q\\\"t\"", ";xyz=1;ijk=q\"t");
         ce(";x;y");
 
+		ce(";chunked;a=b;i=j;gzip;windowBits=12");
+		ce(";chunked;a=b;i=j;gzip;windowBits=12;permessage-deflate");
+
         // invalid strings
         cs(";", "");
         cs(";,", "");
@@ -96,6 +99,7 @@ public:
         cq(";xy=\"\x7f", "");
         cq(";xy=\"\\", "");
         cq(";xy=\"\\\x01\"", "");
+
     }
 
     static
@@ -344,11 +348,9 @@ public:
     run()
     {
         testOptTokenList();
-#if 0
         testParamList();
         testExtList();
         testTokenList();
-#endif
     }
 };