Fix webp and brotli status variable in configure

We are interested in webp_ok and brotli_ok which indicates if we can use
webp or brotli. Even if the user specifies --enable-webp setting
enable_webp to yes, if it is not found it won't be available.

Author: rodarima

configure.ac

@@ -825,8 +825,8 @@ _AS_ECHO([  JPEG enabled   : ${jpeg_ok}])
 _AS_ECHO([  PNG enabled    : ${png_ok}])
 _AS_ECHO([  GIF enabled    : ${enable_gif}])
 _AS_ECHO([  SVG enabled    : ${enable_svg}])
-_AS_ECHO([  WEBP enabled   : ${enable_webp}])
-_AS_ECHO([  Brotli enabled : ${enable_brotli}])
+_AS_ECHO([  WEBP enabled   : ${webp_ok}])
+_AS_ECHO([  Brotli enabled : ${brotli_ok}])
 _AS_ECHO([])
 _AS_ECHO([  HTML tests     : ${html_tests_ok}])
 _AS_ECHO([])