Added libestr dependency to librsyslog_la automake target

When using LIBESTR_CFLAGS and LIBESTR_LIBS directly, build fails without this.
Added LIBLOGGING_STDLOG_CFLAGS and LIBLOGGING_STDLOG_LIBS to automake sources

Build was failing when using these variables
Merge pull request #128 from kuna-systems/master

Added libestr dependency to librsyslog_la automake target