file.c: move chmod, fchmod, and fchmodat parsers to a separate file

* chmod.c: New file.
* Makefile.am (strace_SOURCES): Add it.
* file.c (sys_chmod, sys_fchmodat, sys_fchmod): Move to chmod.c.
diff --git a/chmod.c b/chmod.c
new file mode 100644
index 0000000..89453a9
--- /dev/null
+++ b/chmod.c
@@ -0,0 +1,35 @@
+#include "defs.h"
+
+static int
+decode_chmod(struct tcb *tcp, int offset)
+{
+	if (entering(tcp)) {
+		printpath(tcp, tcp->u_arg[offset]);
+		tprintf(", %#lo", tcp->u_arg[offset + 1]);
+	}
+	return 0;
+}
+
+int
+sys_chmod(struct tcb *tcp)
+{
+	return decode_chmod(tcp, 0);
+}
+
+int
+sys_fchmodat(struct tcb *tcp)
+{
+	if (entering(tcp))
+		print_dirfd(tcp, tcp->u_arg[0]);
+	return decode_chmod(tcp, 1);
+}
+
+int
+sys_fchmod(struct tcb *tcp)
+{
+	if (entering(tcp)) {
+		printfd(tcp, tcp->u_arg[0]);
+		tprintf(", %#lo", tcp->u_arg[1]);
+	}
+	return 0;
+}