library: ensure 'namespace' types treated consistently

Unlike the ps kludge under the master branch to ensure
that namespaces appear the same under both 32 & 64-bit
models, this newlib branch already used a proper type.

However source data still carried the original type as
'signed long' versus that more proper 'unsigned long'.

So, this patch makes sources & destinations identical.

Reference(s):
. master branch ps kludge
commit c41c614b0c

Signed-off-by: Jim Warner <james.warner@comcast.net>

proc/namespace.h

@@ -36,7 +36,7 @@ enum namespace_type {
 };
 
 struct procps_namespaces {
-    long ns[PROCPS_NS_COUNT];
+    unsigned long ns[PROCPS_NS_COUNT];
 };
 
 const char *procps_ns_get_name(const int id);