Update docs and tests for bro_(init|done) -> zeek_(init|done)

testing/btest/scripts/base/files/extract/limit.bro

@@ -39,7 +39,7 @@ event file_extraction_limit(f: fa_file, args: any, limit: count, len: count)
 		print outfile, FileExtract::set_limit(f, args, 0);
     }
 
-event bro_init()
+event zeek_init()
 	{
 	outfile = open(fmt("%s.out", efname));
 	}

testing/btest/scripts/base/files/x509/signed_certificate_timestamp_ocsp.test

@@ -1,7 +1,7 @@
 # @TEST-EXEC: bro -r $TRACES/tls/signed_certificate_timestamp.pcap %INPUT
 # @TEST-EXEC: btest-diff .stdout
 
-event bro_init()
+event zeek_init()
 	{
 	Files::register_for_mime_type(Files::ANALYZER_OCSP_REPLY, "application/ocsp-response");
 	}