POSIX says `struct timeval` is only defined if <sys/time.h> is included.

So include it.

--- libnfs-libnfs-3.0.0/include/nfsc/libnfs.h.old	2018-06-23 22:53:52.000000000 +0000
+++ libnfs-libnfs-3.0.0/include/nfsc/libnfs.h	2018-07-27 09:11:13.200000000 +0000
@@ -24,12 +24,8 @@
 #define _LIBNFS_H_
 
 #include <stdint.h>
-#if defined(__ANDROID__) || defined(AROS) \
- || ( defined(__APPLE__) && defined(__MACH__) )
 #include <sys/time.h>
-#else
 #include <time.h>
-#endif
 
 #ifdef __cplusplus
 extern "C" {