[mod_deflate] fix choose encoding parse error (fixes #2981)

regression in mod_deflate in lighttpd 1.4.54

(thx ocin)

x-ref:
  "mod_deflate_choose_encoding() parse error"
  https://redmine.lighttpd.net/issues/2981

src/mod_deflate.c

@@ -997,7 +997,7 @@ static int mod_deflate_choose_encoding (const char *value, plugin_data *p, const
       #else
         for (; *value; ++value) {
             const char *v;
-            while (*value == ' ' || *value == ',') continue;
+            while (*value == ' ' || *value == ',') ++value;
             v = value;
             while (*value!=' ' && *value!=',' && *value!=';' && *value!='\0')
                 ++value;