variables aren't used uninitialized.
* error.h (scm_error, scm_syserror, scm_syserror_msg,
scm_sysmissing, scm_num_overflow, scm_out_of_range,
scm_wrong_num_args, scm_wrong_type_arg, scm_memory_error,
scm_misc_error): Tell GCC that these functions never return.
* struct.c (scm_struct_ref, scm_struct_set_x): If we can't figure
out the field type, call abort if SCM_ASSERT returns, to placate
the optimizer.
* stacks.c (scm_make_stack, scm_last_stack_frame): abort if
scm_wta ever returns. We can't handle this case anyway, and this
gives the optimizer more information.
* unif.c (scm_uniform_vector_ref, scm_array_set_x): Abort if
scm_wta ever returns.
number of stack narrowing specifier pairs. The first specifier in
a pair controls inner border, the second the outer border. A
number means cut that number of frames, a procedure object means
cut until that object is found in operator position in a frame.
a stack object. Introduce one level of indirection in the stack
object to make it possible to "narrow" to a certain region of the
stack. This facilitates making use of more clever algorithms (not
implemented) for selecting relevant frames and gives a cleaner
design since selection of frames can be done independently of
extraction of frames from the real stack.
(scm_stack_id): Also take #t as argument which means look at
current stack.
