httpd: shrink mime type matching code (suggested by Bernhard)

httpd: shrink mime type matching code (suggested by Bernhard)

function                                             old     new   delta
static.suffixTable                                   100     231    +131
send_file_and_exit                                   625     658     +33
handle_incoming_and_exit                            2749    2745      -4
send_cgi_and_exit                                    936     901     -35
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 2/2 up/down: 164/-39)           Total: 125 bytes
   text    data     bss     dec     hex filename
 824631     458    6956  832045   cb22d busybox_old
 824550     458    6956  831964   cb1dc busybox_unstripped

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>