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/escape.h

@@ -1,11 +1,8 @@
 #ifndef PROCPS_PROC_ESCAPE_H
 #define PROCPS_PROC_ESCAPE_H
 
-#include <features.h>
 #include "readproc.h"
 
-__BEGIN_DECLS
-
 
 #define ESC_ARGS     0x1  // try to use cmdline instead of cmd
 #define ESC_BRACKETS 0x2  // if using cmd, put '[' and ']' around it
@@ -14,5 +11,4 @@ __BEGIN_DECLS
 
 int escape_command(char *__restrict const outbuf, const proc_t *__restrict const pp, int bytes, int *cells, unsigned flags);
 
-__END_DECLS
 #endif