fix all missing instances of __cplusplus checks/extern "C" in headers

patch by Arvid Picciani (aep)

include/sys/resource.h

@@ -1,6 +1,10 @@
 #ifndef	_SYS_RESOURCE_H
 #define	_SYS_RESOURCE_H
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 #define __NEED_id_t
 #define __NEED_time_t
 #define __NEED_struct_timeval
@@ -76,4 +80,8 @@ int setpriority (int, id_t, int);
 #define RLIM_NLIMITS RLIMIT_NLIMITS
 
 
+#ifdef __cplusplus
+}
+#endif
+
 #endif