Add cache support for some values which require running on the
target. These need to be set in the site files:

 cherokee_cv_have_epoll
 cherokee_cv_func_sendfile_works

Both should be set to yes for any reasonably recent linux.

Index: cherokee-0.5.5/configure.in
===================================================================
--- cherokee-0.5.5.orig/configure.in
+++ cherokee-0.5.5/configure.in
@@ -280,6 +280,7 @@ have_epoll=no
 if test "x$have_epoll_include" = "xyes"; then
  	AC_MSG_CHECKING(for epoll system call)
 
+     AC_CACHE_CHECK([for epoll],cherokee_cv_have_epoll,[
      AC_TRY_RUN([
 		#include <stdint.h>
 		#include <sys/param.h>
@@ -297,8 +298,7 @@ if test "x$have_epoll_include" = "xyes";
 	        epfd = epoll_create(256);
 	    	   exit (epfd == -1 ? 1 : 0);
 		}
-	], have_epoll=yes)
-	AC_MSG_RESULT($have_epoll)
+	], have_epoll=yes)])
 fi
 
 dnl
@@ -625,16 +625,16 @@ ETR_SOCKET_NSL
 SENDFILE_CHECK
 
 # Is sendfile broken?
-AC_MSG_CHECKING(if sendfile works)
+AC_CACHE_CHECK([if sendfile works],cherokee_cv_func_sendfile_works,[
 AC_TRY_RUN([#include <errno.h>
             int main() {
                int o = 0;
                if (-1 == sendfile(0, 0, &o, 0) && errno == ENOSYS) return -1;
                return 0;
-            } ], 
-            AC_MSG_RESULT(yes), 
-            [ AC_MSG_RESULT(no) 
-              AC_DEFINE([HAVE_SENDFILE_BROKEN], [1], [broken sendfile]) ])
+            } ], cherokee_cv_func_sendfile_works=yes,cherokee_cv_func_sendfile_works=no,cherokee_cv_func_sendfile_works=no)])
+if test "$cherokee_cv_func_sendfile_works" = no; then
+        AC_DEFINE([HAVE_SENDFILE_BROKEN], [1], [broken sendfile])
+fi
 
 # readdir_r()
 LIBWWW_READDIR_R_TYPE