libkmod: add finit_module logic

When a module is being loaded directly from disk (no compression, etc),
pass the file descriptor to the new finit_module() syscall. If the
finit_module syscall is exported by the kernel syscall headers, use it.
Additionally, if the kernel's module.h file is available, map kmod flags
to finit_module flags.
diff --git a/configure.ac b/configure.ac
index 0f86c25..566b317 100644
--- a/configure.ac
+++ b/configure.ac
@@ -43,6 +43,9 @@
 # dietlibc doesn't have st.st_mtim struct member
 AC_CHECK_MEMBERS([struct stat.st_mtim], [], [], [#include <sys/stat.h>])
 
+# Check kernel headers
+AC_CHECK_HEADERS_ONCE([linux/module.h])
+
 
 #####################################################################
 # --with-