Add repo specific errors

1. Add Internal.errors.yaml to define repo specific errors
2. Update configure.ac and Makefile.am to generate code from error yamls
3. Add elog-gen.hpp generated by elog-gen.py

Change-Id: I6858f2c9f3c2100ce106d1effe7ad3f340117fec
Signed-off-by: Lei YU <mine260309@gmail.com>
diff --git a/xyz/openbmc_project/Time/Internal.errors.yaml b/xyz/openbmc_project/Time/Internal.errors.yaml
new file mode 100644
index 0000000..a2502ab
--- /dev/null
+++ b/xyz/openbmc_project/Time/Internal.errors.yaml
@@ -0,0 +1,3 @@
+#xyz.openbmc_project.Time.Internal.MethodError
+- name: MethodError
+  description: Failed to invoke Dbus method