Core: fixed comment about escaping in arguments.

After 4954530db2af, the ";" character is escaped by
ngx_escape_uri(NGX_ESCAPE_ARGS).

src/core/ngx_string.c

diff --git a/src/core/ngx_string.c b/src/core/ngx_string.c
index 5cc9b26..7ed3463 100644
--- a/src/core/ngx_string.c
+++ b/src/core/ngx_string.c
@@ -1513,7 +1513,7 @@
         0xffffffff  /* 1111 1111 1111 1111  1111 1111 1111 1111 */
     };
 
-                    /* " ", "#", "%", "&", "+", "?", %00-%1F, %7F-%FF */
+                    /* " ", "#", "%", "&", "+", ";", "?", %00-%1F, %7F-%FF */
 
     static uint32_t   args[] = {
         0xffffffff, /* 1111 1111 1111 1111  1111 1111 1111 1111 */