library: eliminate inappropriate '__BEGIN_DECLS' macro

This patch simply eliminates that glibc specific macro
from all header files which contain no public callable
functions. After all, if user code can't link to them,
then protection from C++ name mangling is unnecessary.

[ we also remove any related '#include <features.h>' ]

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

proc/numa.h

@@ -20,16 +20,10 @@
 #ifndef PROCPS_NUMA_H
 #define PROCPS_NUMA_H
 
-#include <features.h>
-
-__BEGIN_DECLS
-
 void numa_init (void);
 void numa_uninit (void);
 
 extern int (*numa_max_node) (void);
 extern int (*numa_node_of_cpu) (int);
 
-__END_DECLS
-
 #endif