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/storage/MemoryDirectoryReader.cxx

@@ -19,7 +19,7 @@
 
 #include "MemoryDirectoryReader.hxx"
 
-#include <assert.h>
+#include <cassert>
 
 const char *
 MemoryStorageDirectoryReader::Read() noexcept

src/storage/plugins/CurlStorage.cxx

@@ -41,12 +41,11 @@
 #include "util/StringFormat.hxx"
 #include "util/UriExtract.hxx"
 
+#include <cassert>
 #include <memory>
 #include <string>
 #include <utility>
 
-#include <assert.h>
-
 class CurlStorage final : public Storage {
 	const std::string base;
 

src/storage/plugins/NfsStorage.cxx

@@ -42,9 +42,9 @@ extern "C" {
 #include <nfsc/libnfs-raw-nfs.h>
 }
 
+#include <cassert>
 #include <string>
 
-#include <assert.h>
 #include <sys/stat.h>
 #include <fcntl.h>