add init_module/delete_module syscall wrappers

these are not exposed publicly in any header, but the few programs
that use them (modutils/kmod, etc.) are declaring the functions
themselves rather than making the syscalls directly, and it doesn't
really hurt to have them (same as the capset junk).

src/linux/module.c

+#include "syscall.h"
+
+int init_module(void *a, unsigned long b, const char *c)
+{
+	return syscall(SYS_init_module, a, b, c);
+}
+
+int delete_module(const char *a, unsigned b)
+{
+	return syscall(SYS_delete_module, a, b);
+}