Warning fixes from Greg Harvey:

Warning fixes from Greg Harvey:
* unif.c (scm_array_set_x): initializer for pos
* throw.c (scm_ithrow): added initializer for jmpbuf (SCM_UNDEFINED)
* struct.c (scm_struct_ref, scm_struct_set_x): Added
initializers for field_type, since EGCS so desparately wants to
play dumb
* debug.h (scm_make_gloc, scm_gloc_p, scm_make_iloc, scm_memcons,
scm_mem_to_proc, scm_proc_to_mem, scm_debug_hang): Added prototypes
when GUILE_DEBUG is defined.
* dynwind.h (scm_wind_chain): Same.
* ports.h (scm_pt_size, scm_pt_member): Same.
* print.h (scm_current_pstate): Same.
* procs.h (scm_make_cclo): Same.