BUG/MINOR: http-htx: Do case-insensive comparisons on Host header name

When a header is added or modified, in http_add_header() or
http_replace_header(), a comparison is performed on its name to know if it is
the Host header and if the authority part of the uri must be updated or
not. This comparision must be case-insensive.

This patch should fix the issue #522. It must be backported to 2.1.
diff --git a/src/http_htx.c b/src/http_htx.c
index d523967..35bb056 100644
--- a/src/http_htx.c
+++ b/src/http_htx.c
@@ -215,7 +215,7 @@
 
   end:
 	sl = http_get_stline(htx);
-	if (sl && (sl->flags & HTX_SL_F_HAS_AUTHORITY) && isteq(n, ist("host"))) {
+	if (sl && (sl->flags & HTX_SL_F_HAS_AUTHORITY) && isteqi(n, ist("host"))) {
 		if (!http_update_authority(htx, sl, v))
 			goto fail;
 	}
@@ -491,7 +491,7 @@
 		goto fail;
 
 	sl = http_get_stline(htx);
-	if (sl && (sl->flags & HTX_SL_F_HAS_AUTHORITY) && isteq(name, ist("host"))) {
+	if (sl && (sl->flags & HTX_SL_F_HAS_AUTHORITY) && isteqi(name, ist("host"))) {
 		if (!http_update_authority(htx, sl, value))
 			goto fail;
 		ctx->blk = NULL;