Make pid2tcb static

* defs.h: Remove pid2tcb declaration.
* strace.c (pid2tcb): Make this function static.

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/strace.c b/strace.c
index 20c0266..782fe8f 100644
--- a/strace.c
+++ b/strace.c
@@ -1607,7 +1607,7 @@
 
 #endif /* USE_PROCFS */
 
-struct tcb *
+static struct tcb *
 pid2tcb(int pid)
 {
 	int i;