Add a parameter to set the size of the stack buffers we use for gzip

processing.

bin/varnishd/heritage.h

@@ -200,6 +200,7 @@ struct params {
 	unsigned		http_range_support;
 
 	unsigned		http_gzip_support;
+	unsigned		gzip_stack_buffer;
 
 	double			critbit_cooloff;
 };

bin/varnishd/mgt_param.c

@@ -817,6 +817,11 @@ static const struct parspec input_parspec[] = {
 		"Enable support for HTTP GZIP compression.\n",
 		EXPERIMENTAL,
 		"off", "bool" },
+	{ "gzip_stack_buffer", tweak_uint, &master.gzip_stack_buffer,
+	        4, UINT_MAX,
+		"Size of stack buffer used for gzip processing.\n",
+		EXPERIMENTAL,
+		"64", "Kilobytes" },
 	{ "critbit_cooloff", tweak_timeout_double,
 		&master.critbit_cooloff, 60, 254,
 		"How long time the critbit hasher keeps deleted objheads "