Move process-related functions and structures to proc.h
diff --git a/sysdeps/linux-gnu/proc.c b/sysdeps/linux-gnu/proc.c
index 3350117..eba030f 100644
--- a/sysdeps/linux-gnu/proc.c
+++ b/sysdeps/linux-gnu/proc.c
@@ -18,6 +18,7 @@
 
 #include "common.h"
 #include "breakpoint.h"
+#include "proc.h"
 
 /* /proc/pid doesn't exist just after the fork, and sometimes `ltrace'
  * couldn't open it to find the executable.  So it may be necessary to