virtiofsd: Add auxiliary .c's

Add most of the non-main .c files we need from upstream fuse-3.8.0

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

tools/virtiofsd/fuse_log.c

@@ -0,0 +1,40 @@
+/*
+  FUSE: Filesystem in Userspace
+  Copyright (C) 2019  Red Hat, Inc.
+
+  Logging API.
+
+  This program can be distributed under the terms of the GNU LGPLv2.
+  See the file COPYING.LIB
+*/
+
+#include "fuse_log.h"
+
+#include <stdarg.h>
+#include <stdio.h>
+
+static void default_log_func(
+		__attribute__(( unused )) enum fuse_log_level level,
+		const char *fmt, va_list ap)
+{
+	vfprintf(stderr, fmt, ap);
+}
+
+static fuse_log_func_t log_func = default_log_func;
+
+void fuse_set_log_func(fuse_log_func_t func)
+{
+	if (!func)
+		func = default_log_func;
+
+	log_func = func;
+}
+
+void fuse_log(enum fuse_log_level level, const char *fmt, ...)
+{
+	va_list ap;
+
+	va_start(ap, fmt);
+	log_func(level, fmt, ap);
+	va_end(ap);
+}