Merge pull request #131 from jsonng/patch-1

Update to include access control allow origin

Author: ras0219-msft

Release/include/cpprest/details/http_constants.dat

@@ -60,6 +60,7 @@ DAT(accept_charset,         "Accept-Charset")
 DAT(accept_encoding,        "Accept-Encoding")
 DAT(accept_language,        "Accept-Language")
 DAT(accept_ranges,          "Accept-Ranges")
+DAT(access_control_allow_origin,  "Access-Control-Allow-Origin")
 DAT(age,                    "Age")
 DAT(allow,                  "Allow")
 DAT(authorization,          "Authorization")