FEATURE Add NETCONF time function

Add implementation of public functions to work with timestamps in the
NETCONF format.
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 576a7eb..2d82901 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -32,7 +32,8 @@
 set(CMAKE_C_FLAGS_DEBUG   "-g -O0")
 
 set(libsrc
-	src/log.c)
+	src/log.c
+	src/time.c)
 
 set(headers
 	src/log.h)