src: add libosmo_abis_init(void *ctx) to set the talloc context

This function is called during initialization, so we can set what's
the talloc context for the application and the library.
diff --git a/include/osmocom/abis/abis.h b/include/osmocom/abis/abis.h
new file mode 100644
index 0000000..af8c64c
--- /dev/null
+++ b/include/osmocom/abis/abis.h
@@ -0,0 +1,6 @@
+#ifndef _OSMO_ABIS_H_
+#define _OSMO_ABIS_H_
+
+void libosmo_abis_init(void *ctx);
+
+#endif