Add generic LOG() macro with level parameter

One log macro was provided for each log level (LOGV(), LOGD(), LOGI(),
LOGW(), LOGE()).

Add a generic macro LOG(LEVEL, ...) taking a log level as parameter, so
that it is possible to write logging wrappers.

app/src/util/log.h

@@ -25,6 +25,10 @@ sc_set_log_level(enum sc_log_level level);
 enum sc_log_level
 sc_get_log_level(void);
 
+void
+sc_log(enum sc_log_level level, const char *fmt, ...);
+#define LOG(LEVEL, ...) sc_log((LEVEL), __VA_ARGS__)
+
 #ifdef _WIN32
 // Log system error (typically returned by GetLastError() or similar)
 bool