maint: trivial system header file cleanups

* src/system.h: Note where it should be included, and
make ordering check portable to GLIBC > 2
* src/copy.c: Move <sys/ioctl.h> along with other system headers
as is done elsewhere.
* src/install.c: Move <sys/wait.h> along with other system headers
as is done elsewhere.
* src/ptx.c: Include <regex.h> rather than "regex.h" as
is done elsewhere.  Note <regex.h> is kept after "system.h"
as per commit dba300a0.

1 files changed, 1 insertions, 1 deletions

diff --git a/src/ptx.c b/src/ptx.c
index 940f6e84e..646561842 100644
--- a/src/ptx.c
+++ b/src/ptx.c
@@ -22,13 +22,13 @@
 #include <getopt.h>
 #include <sys/types.h>
 #include "system.h"
+#include <regex.h>
 #include "argmatch.h"
 #include "diacrit.h"
 #include "error.h"
 #include "fadvise.h"
 #include "quote.h"
 #include "quotearg.h"
-#include "regex.h"
 #include "stdio--.h"
 #include "xstrtol.h"