spa: add debug log context

Make a real debug context with a log function and move it to a new file.
This way we don't need to redefine a macro.
Make a new context for debugging to a log file. Make new functions to
debug to a log file.
Move the stringbuffer to string utils.
Integrate file/line/func and topics into the debug log.
We can remove some more things from the pipewire log_object function and
also add support for topics.

spa/include/spa/debug/context.h

@@ -0,0 +1,62 @@
+/* Simple Plugin API
+ *
+ * Copyright © 2023 Wim Taymans
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+ * DEALINGS IN THE SOFTWARE.
+ */
+
+#ifndef SPA_DEBUG_CONTEXT_H
+#define SPA_DEBUG_CONTEXT_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#include <stdio.h>
+#include <stdarg.h>
+
+#include <spa/utils/defs.h>
+/**
+ * \addtogroup spa_debug
+ * \{
+ */
+
+#ifndef spa_debugn
+#define spa_debugn(_fmt,...)	printf((_fmt), ## __VA_ARGS__)
+#endif
+#ifndef spa_debug
+#define spa_debug(_fmt,...)	spa_debugn(_fmt"\n", ## __VA_ARGS__)
+#endif
+
+struct spa_debug_context {
+	void (*log) (struct spa_debug_context *ctx, const char *fmt, ...) SPA_PRINTF_FUNC(2, 3);
+};
+
+#define spa_debugc(_c,_fmt,...)	(_c)?((_c)->log((_c),_fmt, ## __VA_ARGS__)):(void)spa_debug(_fmt, ## __VA_ARGS__)
+
+/**
+ * \}
+ */
+
+#ifdef __cplusplus
+}  /* extern "C" */
+#endif
+
+#endif /* SPA_DEBUG_CONTEXT_H */