ptrace: print PTRACE_O_* flags using printflags64

As flags argument has a long integer type, print it using printflags64
because printflags takes unsigned int argument.

* process.c (SYS_FUNC(ptrace)): Print PTRACE_O_* flags
using printflags64.
diff --git a/process.c b/process.c
index 5133865..cb0125c 100644
--- a/process.c
+++ b/process.c
@@ -188,7 +188,7 @@
 #ifdef PTRACE_OLDSETOPTIONS
 		case PTRACE_OLDSETOPTIONS:
 #endif
-			printflags(ptrace_setoptions_flags, data, "PTRACE_O_???");
+			printflags64(ptrace_setoptions_flags, data, "PTRACE_O_???");
 			break;
 		case PTRACE_SETSIGINFO:
 			printsiginfo_at(tcp, data);