Fix remaning compilation warning when MIME_MAGIC_DEBUG is defined.

Style is not perfect, but at least, the warning is fixed.

warning: format ‘%c’ expects argument of type ‘int’, but argument 10 has type ‘long unsigned int’ [-Wformat=]

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1805493 13f79535-47bb-0310-9956-ffa450edef68