Deprecate wrappers around loglevel_strs

Add deprecation notice for public API use: it shouldn't be used outside
of libosmocore anyway.

Change-Id: I792e30dc44f027fd94e1f65af19fe08bac52b95c
Related: OS#71
diff --git a/include/osmocom/core/logging.h b/include/osmocom/core/logging.h
index 68a9c13..e058a57 100644
--- a/include/osmocom/core/logging.h
+++ b/include/osmocom/core/logging.h
@@ -306,8 +306,8 @@
 void log_set_log_level(struct log_target *target, int log_level);
 void log_parse_category_mask(struct log_target *target, const char* mask);
 const char* log_category_name(int subsys);
-int log_parse_level(const char *lvl);
-const char *log_level_str(unsigned int lvl);
+int log_parse_level(const char *lvl) OSMO_DEPRECATED_OUTSIDE_LIBOSMOCORE;
+const char *log_level_str(unsigned int lvl) OSMO_DEPRECATED_OUTSIDE_LIBOSMOCORE;
 int log_parse_category(const char *category);
 void log_set_category_filter(struct log_target *target, int category,
 			       int enable, int level);