include cleanup using iwyu

src/system/EPollFD.hxx

@@ -23,6 +23,7 @@
 #include <assert.h>
 #include <sys/epoll.h>
 #include <unistd.h>
+#include <stdint.h>
 
 #include "check.h"
 

src/system/Resolver.cxx

@@ -27,6 +27,9 @@
 #ifndef WIN32
 #include <sys/socket.h>
 #include <netdb.h>
+#ifdef HAVE_TCP
+#include <netinet/in.h>
+#endif
 #else
 #include <ws2tcpip.h>
 #include <winsock.h>

src/system/Resolver.hxx

@@ -27,8 +27,9 @@
 struct sockaddr;
 struct addrinfo;
 class Error;
+class Domain;
 
-extern const class Domain resolver_domain;
+extern const Domain resolver_domain;
 
 /**
  * Converts the specified socket address into a string in the form
@@ -42,7 +43,7 @@ extern const class Domain resolver_domain;
  */
 gcc_malloc
 char *
-sockaddr_to_string(const struct sockaddr *sa, size_t length, Error &error);
+sockaddr_to_string(const sockaddr *sa, size_t length, Error &error);
 
 /**
  * Resolve a specification in the form "host", "host:port",
@@ -54,7 +55,7 @@ sockaddr_to_string(const struct sockaddr *sa, size_t length, Error &error);
  * @return an #addrinfo linked list that must be freed with
  * freeaddrinfo(), or NULL on error
  */
-struct addrinfo *
+addrinfo *
 resolve_host_port(const char *host_port, unsigned default_port,
 		  int flags, int socktype,
 		  Error &error);

src/system/SignalFD.cxx

@@ -20,7 +20,6 @@
 #include "config.h"
 #ifdef USE_SIGNALFD
 #include "SignalFD.hxx"
-#include "fd_util.h"
 #include "FatalError.hxx"
 
 #include <assert.h>

src/system/SocketError.hxx

@@ -21,7 +21,7 @@
 #define MPD_SOCKET_ERROR_HXX
 
 #include "Compiler.h"
-#include "util/Error.hxx"
+#include "util/Error.hxx" // IWYU pragma: export
 
 #ifdef WIN32
 #include <winsock2.h>
@@ -31,11 +31,13 @@ typedef DWORD socket_error_t;
 typedef int socket_error_t;
 #endif
 
+class Domain;
+
 /**
  * A #Domain for #Error for socket I/O errors.  The code is an errno
  * value (or WSAGetLastError() on Windows).
  */
-extern const class Domain socket_domain;
+extern const Domain socket_domain;
 
 gcc_pure
 static inline socket_error_t