cut off 'curl_' from the strerror file names

lib/Makefile.am

@@ -75,7 +75,7 @@ libcurl_la_SOURCES = arpa_telnet.h file.c netrc.h timeval.c base64.c	\
   content_encoding.c content_encoding.h share.c share.h http_digest.c	\
   md5.c md5.h http_digest.h http_negotiate.c http_negotiate.h		\
   http_ntlm.c http_ntlm.h ca-bundle.h inet_pton.c inet_pton.h		\
-  strtoofft.c strtoofft.h curl_strerror.c curl_strerror.h
+  strtoofft.c strtoofft.h strerror.c strerror.h
 
 noinst_HEADERS = setup.h transfer.h