Make allowing gzip a Makefile tunable

Makefile

@@ -4,11 +4,13 @@ CC?=gcc
 #FEATURES+=-DWANT_CLOSED_TRACKER
 #FEATURES+=-DWANT_UTORRENT1600_WORKAROUND
 #FEATURES+=-DWANT_IP_FROM_QUERY_STRING
+#FEATURES+=-DWANT_COMPRESSION_GZIP 
 #FEATURES+=-D_DEBUG_HTTPERROR
+
 OPTS_debug=-g -ggdb #-pg # -fprofile-arcs -ftest-coverage
 OPTS_production=-Os
 CFLAGS+=-I../libowfat -Wall -pipe -Wextra #-pedantic -ansi
-LDFLAGS+=-L../libowfat/ -lowfat -pthread
+LDFLAGS+=-L../libowfat/ -lowfat -pthread -lz
 
 BINARY =opentracker
 HEADERS=trackerlogic.h scan_urlencoded_query.h ot_mutex.h ot_stats.h ot_sync.h ot_vector.h ot_clean.h ot_udp.h ot_iovec.h ot_fullscrape.h ot_accesslist.h