Fixed dnslib error messages.

- The file was not compiled at all.
- Had to rename it to dnslib-error.c, as it is impossible to have
  more source files with the same name in the project (Makefile
  issues).

Knot.files

@@ -36,7 +36,7 @@ src/dnslib/dname.h
 src/dnslib/dname.c
 src/dnslib/rrset.h
 src/dnslib/rrset.c
-src/dnslib/error.c
+src/dnslib/dnslib-error.c
 src/dnslib/error.h
 src/dnslib/rdata.h
 src/dnslib/rdata.c

src/Makefile.am

@@ -118,6 +118,7 @@ libknot_la_SOURCES =				\
 	knot/stat/gatherer.h				\
 	knot/stat/stat.h				\
 	dnslib/edns.c                           \
+	dnslib/dnslib-error.c			\
 	dnslib/utils.c				\
 	dnslib/rrset.c				\
 	dnslib/dname.c				\