Log extensions: series of small fixes and new tests.

The extensions now work with optional types, as well with complex types
(like subrecords). Not returning a record in the ext_func no longer
crashes bro.

The default_ext_func was switched to return void in
cases where no extension revord is defined (was bool).

I also got rid of the offsets in the indices - with the rest of the
implementation, that was not really necessary and made the code more
complex.

testing/btest/scripts/base/frameworks/logging/field-extension-complex.bro

@@ -0,0 +1,37 @@
+# @TEST-EXEC: bro -b -r $TRACES/wikipedia.trace %INPUT
+# @TEST-EXEC: btest-diff conn.log
+
+@load base/protocols/conn
+
+type InnerRecord: record {
+	a: count;
+	b: count;
+	c: count;
+};
+
+type InnerLoggedRecord: record {
+	a: count &log;
+	b: count;
+	c: count &log;
+	d: set[count] &log;
+};
+
+type Extension: record {
+	write_ts: time &log;
+	stream: string &log;
+	inner: InnerRecord;
+	innerLogged: InnerLoggedRecord &log;
+	system_name: string &log;
+};
+
+function add_extension(path: string): Extension
+	{
+	return Extension($write_ts    = network_time(),
+	                 $stream      = path,
+	                 $system_name = peer_description,
+									 $inner = InnerRecord($a=1,$b=2,$c=3),
+									 $innerLogged = InnerLoggedRecord($a=1,$b=2,$c=3,$d=set(1,2,3,4))
+									 );
+	}
+
+redef Log::default_ext_func = add_extension;

testing/btest/scripts/base/frameworks/logging/field-extension-invalid.bro

@@ -0,0 +1,17 @@
+# @TEST-EXEC: bro -b -r $TRACES/http/get.trace %INPUT
+# @TEST-EXEC: btest-diff conn.log
+# @TEST-EXEC: btest-diff .stderr
+
+@load base/protocols/conn
+
+type Extension: record {
+	write_ts: time &log;
+	stream: string &log;
+	system_name: string &log;
+};
+
+function add_extension(path: string): Extension
+	{
+	}
+
+redef Log::default_ext_func = add_extension;

testing/btest/scripts/base/frameworks/logging/field-extension-optional.bro

@@ -0,0 +1,20 @@
+# @TEST-EXEC: bro -b -r $TRACES/wikipedia.trace %INPUT
+# @TEST-EXEC: btest-diff conn.log
+
+@load base/protocols/conn
+
+type Extension: record {
+	write_ts: time &log;
+	stream: string;
+	system_name: string &log &optional;
+	undefined_string: string &log &optional;
+};
+
+function add_extension(path: string): Extension
+	{
+	return Extension($write_ts    = network_time(),
+	                 $stream      = path,
+	                 $system_name = peer_description);
+	}
+
+redef Log::default_ext_func = add_extension;

testing/btest/scripts/base/frameworks/logging/field-extension-table.bro

@@ -0,0 +1,22 @@
+# @TEST-EXEC-FAIL: bro -b -r $TRACES/wikipedia.trace %INPUT
+# @TEST-EXEC: TEST_DIFF_CANONIFIER=$SCRIPTS/diff-remove-abspath btest-diff .stderr
+
+@load base/protocols/conn
+
+type Extension: record {
+	write_ts: time &log;
+	stream: string &log;
+	tab: table[count] of count &log;
+	system_name: string &log;
+};
+
+function add_extension(path: string): Extension
+	{
+	return Extension($write_ts    = network_time(),
+	                 $stream      = path,
+	                 $system_name = peer_description,
+	                 $tab         = { [1] = 2, [2] = 3}
+	                 );
+	}
+
+redef Log::default_ext_func = add_extension;