file.c: move open, openat, and creat parsers to a separate file

* open.c: New file.
* Makefile.am (strace_SOURCES): Add it.
* file.c: Move sys_open, sys_openat, sys_creat, and related code
to open.c.
diff --git a/Makefile.am b/Makefile.am
index 06a18bd..ef1f1d0 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -50,6 +50,7 @@
 	mount.c		\
 	mtd.c		\
 	net.c		\
+	open.c		\
 	or1k_atomic.c	\
 	pathtrace.c	\
 	personality.c	\