MINOR: compression: tune.comp.maxlevel

This option allows you to set the maximum compression level usable by
the compression algorithm. It affects CPU usage.
diff --git a/include/types/compression.h b/include/types/compression.h
index fa251f1..da356ad 100644
--- a/include/types/compression.h
+++ b/include/types/compression.h
@@ -44,6 +44,7 @@
 	void *zlib_pending_buf;
 	void *zlib_head;
 #endif /* USE_ZLIB */
+	int cur_lvl;
 };
 
 struct comp_algo {
diff --git a/include/types/global.h b/include/types/global.h
index e4e317b..cfb10d1 100644
--- a/include/types/global.h
+++ b/include/types/global.h
@@ -117,6 +117,7 @@
 		int zlibmemlevel;    /* zlib memlevel */
 		int zlibwindowsize;  /* zlib window size */
 #endif
+		int comp_maxlevel;    /* max HTTP compression level */
 	} tune;
 	struct {
 		char *prefix;           /* path prefix of unix bind socket */