Fix building on ppc64

The type definitions on ppc64 has two forms, the older one that uses long
for 64-bit types and the newer one that uses long long for 64-bit types.

The long long version is what other architectures use and what libbpfgo
expects in e.g. bpfMapCreateOptsToC.

All that's required to enable the latter ABI is to define
__SANE_USERSPACE_TYPES__ when including the type headers.

Fixes: #274

libbpfgo.h

@@ -1,6 +1,10 @@
 #ifndef __LIBBPF_GO_H__
 #define __LIBBPF_GO_H__
 
+#ifdef __powerpc64__
+#define __SANE_USERSPACE_TYPES__ 1
+#endif
+
 #include <errno.h>
 #include <stdlib.h>
 #include <string.h>