libguile/threads.h needs throw.h for `scm_catch_body_t'

[thi]

Index: threads.h
===================================================================
RCS file: /cvs/guile/guile/guile-core/libguile/threads.h,v
retrieving revision 1.10
diff -c -p -w -c -r1.10 threads.h
*** threads.h   2000/03/02 20:54:43     1.10
--- threads.h   2000/03/19 13:29:33
***************
*** 50,55 ****
--- 50,56 ----
  
  #include "libguile/__scm.h"
  #include "libguile/procs.h"
+ #include "libguile/throw.h"
  
  /* smob tags for the thread datatypes */
  extern long scm_tc16_thread;