Fixed missing "static" in declaration of ngx_http_gzip_quantity().

src/http/ngx_http_core_module.c

diff --git a/src/http/ngx_http_core_module.c b/src/http/ngx_http_core_module.c
index bfaa90e..4484a5e 100644
--- a/src/http/ngx_http_core_module.c
+++ b/src/http/ngx_http_core_module.c
@@ -2368,7 +2368,7 @@
 }
 
 
-ngx_uint_t
+static ngx_uint_t
 ngx_http_gzip_quantity(u_char *p, u_char *last)
 {
     u_char      c;