Make folly::Uri::port() return uint16_t instead of uint32_t.

Summary: We can safely assume that ports are always going to be 16bit (TCP or UDP), so no need to have a uint32_t here.

Test Plan: Ran tests in folly/tests.

Reviewed By: tudorb@fb.com

FB internal diff: D973291

folly/Uri.cpp

@@ -79,7 +79,7 @@ Uri::Uri(StringPiece str) : port_(0) {
 
     StringPiece port(authorityMatch[4].first, authorityMatch[4].second);
     if (!port.empty()) {
-      port_ = to<uint32_t>(port);
+      port_ = to<uint16_t>(port);
     }
 
     username_ = submatch(authorityMatch, 1);

folly/Uri.h

@@ -48,7 +48,7 @@ class Uri {
   const fbstring& username() const { return username_; }
   const fbstring& password() const { return password_; }
   const fbstring& host() const { return host_; }
-  uint32_t port() const { return port_; }
+  uint16_t port() const { return port_; }
   const fbstring& path() const { return path_; }
   const fbstring& query() const { return query_; }
   const fbstring& fragment() const { return fragment_; }
@@ -64,7 +64,7 @@ class Uri {
   fbstring username_;
   fbstring password_;
   fbstring host_;
-  uint32_t port_;
+  uint16_t port_;
   fbstring path_;
   fbstring query_;
   fbstring fragment_;