replace assert.h with cassert

The former was deprecated with C++14.

According to the C++11 and C++17 standards, both files are identical.

Signed-off-by: Rosen Penev <rosenp@gmail.com>

src/command/AllCommands.cxx

@@ -48,9 +48,9 @@
 #include "StickerCommands.hxx"
 #endif
 
+#include <cassert>
 #include <iterator>
 
-#include <assert.h>
 #include <string.h>
 
 /*

src/command/CommandListBuilder.hxx

@@ -20,11 +20,10 @@
 #ifndef MPD_COMMAND_LIST_BUILDER_HXX
 #define MPD_COMMAND_LIST_BUILDER_HXX
 
+#include <cassert>
 #include <list>
 #include <string>
 
-#include <assert.h>
-
 class CommandListBuilder {
 	/**
 	 * print OK after each command execution

src/command/FileCommands.cxx

@@ -43,7 +43,8 @@
 #include "thread/Mutex.hxx"
 #include "Log.hxx"
 
-#include <assert.h>
+#include <cassert>
+
 #include <inttypes.h> /* for PRIu64 */
 
 gcc_pure

src/command/MessageCommands.cxx

@@ -25,11 +25,10 @@
 #include "util/ConstBuffer.hxx"
 #include "Partition.hxx"
 
+#include <cassert>
 #include <set>
 #include <string>
 
-#include <assert.h>
-
 CommandResult
 handle_subscribe(Client &client, Request args, Response &r)
 {

src/command/OtherCommands.cxx

@@ -55,7 +55,7 @@
 #include "db/update/Service.hxx"
 #endif
 
-#include <assert.h>
+#include <cassert>
 
 static void
 print_spl_list(Response &r, const PlaylistVector &list)

src/command/Request.hxx

@@ -25,10 +25,9 @@
 #include "Chrono.hxx"
 #include "util/ConstBuffer.hxx"
 
+#include <cassert>
 #include <utility>
 
-#include <assert.h>
-
 class Response;
 
 class Request : public ConstBuffer<const char *> {