Fix build with modern glibc/libtirpc rpcsvc/rquota.h.

The legacy Sun RPC headers named the enum type used by the
struct getquota_rslt::status member "gqr_status", but the
standardized rpcsvc/rquota.h (glibc, libtirpc) names it
"qr_status". When di's configure detects that the struct has
no direct gqr_status member, diquota.c casts to the (now
non-existent) gqr_status type, which fails to compile:

  diquota.c:555:19: error: 'gqr_status' undeclared (first use in this function); did you mean 'qr_status'?

Use the correct qr_status type name.

--- a/diquota.c
+++ b/diquota.c
@@ -552,7 +552,7 @@
 # else
 #  pragma clang diagnostic push
 #  pragma clang diagnostic ignored "-Wsign-conversion"
-  rslt->status = (gqr_status) quotastat;
+  rslt->status = (qr_status) quotastat;
 #  pragma clang diagnostic pop
 # endif
 # if _mem_struct_getquota_rslt_gqr_rquota