spa: group the spa headers into doxygen modules

Subdirectories buffer, control, debug, monitor, pod, support and utils, others
are still missing. Headers are grouped either per subdirectory (e.g. buffer/
gets added to group spa_buffer) or per-file (e.g. spa_json is a separate
group), whatever seemed like the most sensible approach.

spa/include/spa/support/log.h

@@ -34,6 +34,14 @@ extern "C" {
 #include <spa/utils/defs.h>
 #include <spa/utils/hook.h>
 
+/** \defgroup spa_log SPA Logging
+ */
+
+/**
+ * \addtogroup spa_log
+ * \{
+ */
+
 enum spa_log_level {
 	SPA_LOG_LEVEL_NONE = 0,
 	SPA_LOG_LEVEL_ERROR,
@@ -173,6 +181,10 @@ static inline void spa_log_trace_fp (struct spa_log *l, const char *format, ...)
 #define SPA_KEY_LOG_TIMESTAMP		"log.timestamp"		/**< log timestamps */
 #define SPA_KEY_LOG_LINE		"log.line"		/**< log file and line numbers */
 
+/**
+ * \}
+ */
+
 #ifdef __cplusplus
 }  /* extern "C" */
 #endif