Move capget and capset parsers to a separate file

* capability.c: New file.
* Makefile.am (strace_SOURCES): Add it.
* system.c: Move inclusion of headers and macro definitions related
to capget and capset decoding to capability.c.
(print_cap_header, print_cap_data, sys_capget, sys_capset): Move
to capability.c.
diff --git a/Makefile.am b/Makefile.am
index 9efebf1..f0e4e13 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -20,6 +20,7 @@
 	aio.c		\
 	bjm.c		\
 	block.c		\
+	capability.c	\
 	count.c		\
 	desc.c		\
 	dirent.c	\