*: don't include standard C headers inside of extern "C"

Including C headers inside of `extern "C"` breaks use from C++. Hoist
the includes of standard C headers above the block so we don't try
to mangle the stdlib.

I initially tried to scope this with a targeted change but it's too
hard to do correctly that way. This way, we avoid whack-a-mole.

Firefox is working around this in their e21461b7b8b39cc31ba53c47d4f6f310c673ff2f
commit.

Bug: https://bugzilla.mozilla.org/1953080

src/modules/module-avb/internal.h

@@ -5,12 +5,12 @@
 #ifndef AVB_INTERNAL_H
 #define AVB_INTERNAL_H
 
+#include <pipewire/pipewire.h>
+
 #ifdef __cplusplus
 extern "C" {
 #endif
 
-#include <pipewire/pipewire.h>
-
 struct server;
 struct avb_mrp;
 

src/modules/module-client-node/v0/ext-client-node.h

@@ -5,16 +5,16 @@
 #ifndef __PIPEWIRE_EXT_CLIENT_NODE0_H__
 #define __PIPEWIRE_EXT_CLIENT_NODE0_H__
 
-#ifdef __cplusplus
-extern "C" {
-#endif
-
 #include <spa/utils/defs.h>
 #include <spa/param/param.h>
 #include <spa/node/node.h>
 
 #include <pipewire/proxy.h>
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 #define PW_TYPE_INTERFACE_ClientNode            PW_TYPE_INFO_INTERFACE_BASE "ClientNode"
 
 #define PW_VERSION_CLIENT_NODE0		0

src/modules/module-client-node/v0/transport.h

@@ -5,16 +5,16 @@
 #ifndef __PIPEWIRE_CLIENT_NODE0_TRANSPORT_H__
 #define __PIPEWIRE_CLIENT_NODE0_TRANSPORT_H__
 
-#ifdef __cplusplus
-extern "C" {
-#endif
-
 #include <string.h>
 
 #include <spa/utils/defs.h>
 
 #include <pipewire/mem.h>
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 /** information about the transport region \memberof pw_client_node */
 struct pw_client_node0_transport_info {
 	int memfd;		/**< the memfd of the transport area */

src/modules/module-jack-tunnel/weakjack.h

@@ -5,10 +5,6 @@
 #ifndef PIPEWIRE_WEAK_JACK_H
 #define PIPEWIRE_WEAK_JACK_H
 
-#ifdef __cplusplus
-extern "C" {
-#endif
-
 #include "config.h"
 
 #include <dlfcn.h>
@@ -17,6 +13,10 @@ extern "C" {
 #include <jack/transport.h>
 #include <jack/midiport.h>
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 struct weakjack {
 	jack_nframes_t (*cycle_wait) (jack_client_t* client);
 	void (*cycle_signal) (jack_client_t* client, int status);

src/modules/module-protocol-native/connection.h

@@ -5,15 +5,15 @@
 #ifndef PIPEWIRE_PROTOCOL_NATIVE_CONNECTION_H
 #define PIPEWIRE_PROTOCOL_NATIVE_CONNECTION_H
 
-#ifdef __cplusplus
-extern "C" {
-#endif
-
 #include <spa/utils/defs.h>
 #include <spa/utils/hook.h>
 
 #include <pipewire/extensions/protocol-native.h>
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 struct pw_protocol_native_connection_events {
 #define PW_VERSION_PROTOCOL_NATIVE_CONNECTION_EVENTS	0
 	uint32_t version;

src/modules/module-protocol-native/v0/interfaces.h

@@ -5,16 +5,16 @@
 #ifndef PIPEWIRE_INTERFACES_V0_H
 #define PIPEWIRE_INTERFACES_V0_H
 
-#ifdef __cplusplus
-extern "C" {
-#endif
-
 #include <spa/utils/defs.h>
 #include <spa/param/param.h>
 #include <spa/node/node.h>
 
 #include <pipewire/pipewire.h>
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 /** Core */
 
 #define PW_VERSION_CORE_V0			0

src/modules/module-protocol-pulse/manager.h

@@ -5,10 +5,6 @@
 #ifndef PIPEWIRE_MANAGER_H
 #define PIPEWIRE_MANAGER_H
 
-#ifdef __cplusplus
-extern "C" {
-#endif
-
 #include <stdio.h>
 
 #include <spa/utils/defs.h>
@@ -16,6 +12,10 @@ extern "C" {
 
 #include <pipewire/pipewire.h>
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 struct client;
 struct pw_manager_object;
 

src/modules/module-protocol-pulse/pulse-server.h

@@ -5,13 +5,13 @@
 #ifndef PIPEWIRE_PROTOCOL_PULSE_H
 #define PIPEWIRE_PROTOCOL_PULSE_H
 
+#include <spa/utils/defs.h>
+#include <spa/utils/hook.h>
+
 #ifdef __cplusplus
 extern "C" {
 #endif
 
-#include <spa/utils/defs.h>
-#include <spa/utils/hook.h>
-
 #define PW_PROTOCOL_PULSE_DEFAULT_PORT 4713
 #define PW_PROTOCOL_PULSE_DEFAULT_SOCKET "native"
 

src/modules/module-raop/rtsp-client.h

@@ -5,14 +5,14 @@
 #ifndef PIPEWIRE_RTSP_CLIENT_H
 #define PIPEWIRE_RTSP_CLIENT_H
 
-#ifdef __cplusplus
-extern "C" {
-#endif
-
 #include <stdarg.h>
 
 #include <pipewire/pipewire.h>
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 struct pw_rtsp_client;
 
 struct pw_rtsp_client_events {