libweston/log: Add 'wlog' group for weston_log() related functions

This allows a better integration with the documentation of logging
framework.

Signed-off-by: Marius Vlad <marius.vlad@collabora.com>

include/libweston/libweston.h

@@ -1812,6 +1812,9 @@ weston_compositor_set_xkb_rule_names(struct weston_compositor *ec,
 /* String literal of spaces, the same width as the timestamp. */
 #define STAMP_SPACE "               "
 
+/**
+ * \ingroup wlog
+ */
 typedef int (*log_func_t)(const char *fmt, va_list ap);
 void
 weston_log_set_handler(log_func_t log, log_func_t cont);

libweston/log.c

@@ -36,10 +36,23 @@
 
 #include <libweston/libweston.h>
 
+/**
+ * \defgroup wlog weston-logging
+ */
+
 static int
 default_log_handler(const char *fmt, va_list ap);
 
+/** Needs to be set, defaults to default_log_handler
+ *
+ * \ingroup wlog
+ */
 static log_func_t log_handler = default_log_handler;
+
+/** Needs to be set, defaults to default_log_handler
+ *
+ * \ingroup wlog
+ */
 static log_func_t log_continue_handler = default_log_handler;
 
 /** Sentinel log message handler
@@ -51,6 +64,8 @@ static log_func_t log_continue_handler = default_log_handler;
  *
  * \param fmt The format string. Ignored.
  * \param ap The variadic argument list. Ignored.
+ *
+ * \ingroup wlog
  */
 static int
 default_log_handler(const char *fmt, va_list ap)
@@ -71,6 +86,8 @@ default_log_handler(const char *fmt, va_list ap)
  *             when \a weston_log_continue is called, and should append
  *             its output to the current line, without any header or
  *             other content in between.
+ *
+ * \ingroup wlog
  */
 WL_EXPORT void
 weston_log_set_handler(log_func_t log, log_func_t cont)
@@ -79,12 +96,25 @@ weston_log_set_handler(log_func_t log, log_func_t cont)
 	log_continue_handler = cont;
 }
 
+/** weston_vlog calls log_handler
+ * \ingroup wlog
+ */
 WL_EXPORT int
 weston_vlog(const char *fmt, va_list ap)
 {
 	return log_handler(fmt, ap);
 }
 
+/** printf() equivalent in weston compositor.
+ *
+ * \rststar
+ * 	.. note::
+ *
+ * 		Needs :var:`log_handler` to be set-up!
+ * \endrststar
+ *
+ * \ingroup wlog
+ */
 WL_EXPORT int
 weston_log(const char *fmt, ...)
 {
@@ -98,12 +128,20 @@ weston_log(const char *fmt, ...)
 	return l;
 }
 
+/** weston_vlog_continue calls log_continue_handler
+ *
+ * \ingroup wlog
+ */
 WL_EXPORT int
 weston_vlog_continue(const char *fmt, va_list argp)
 {
 	return log_continue_handler(fmt, argp);
 }
 
+/** weston_log_continue
+ *
+ * \ingroup wlog
+ */
 WL_EXPORT int
 weston_log_continue(const char *fmt, ...)
 {