archival: avoid std namespace for local includes

Avoid using same include file naming pattern as available in GLIBC.
Renamed to match grp_.h et al.

Signed-off-by: Joachim Nilsson <troglobit@gmail.com>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

include/ar_.h

@@ -0,0 +1,26 @@
+/*
+ * busybox ar archive data structures
+ * Licensed under GPLv2 or later, see file LICENSE in this source tree.
+ */
+#ifndef AR_H
+#define AR_H
+
+PUSH_AND_SET_FUNCTION_VISIBILITY_TO_HIDDEN
+
+struct ar_header {
+	char name[16];
+	char date[12];
+	char uid[6];
+	char gid[6];
+	char mode[8];
+	char size[10];
+	char magic[2];
+};
+
+#define AR_HEADER_LEN sizeof(struct ar_header)
+#define AR_MAGIC      "!<arch>"
+#define AR_MAGIC_LEN  7
+
+POP_SAVED_FUNCTION_VISIBILITY
+
+#endif