ffi/unsafe/atomic: improve docs
allow mixing exceptions with ffi/unsafe/alloc

Use call-as-atomic that can handle exceptions instead of dynamic-winding
start-atomic and end-atomic. Exceptions can be found in the functions's
result wrapper such as:

    (define-lib find-some-object
                (_fun (name : _string/utf-8)
                      (object : (_ptr o _some-object-pointer))
                      --> (result : _int)
                      --> (begin
                            (when (negative? result)
                              (error 'find-some-object "unknown name"))
                            object))
                #:wrap (allocator free-some-object))

Signed-off-by: Jan Dvořák <mordae@anilinux.org>
mz-gdbinit script gives type when using pso

The mz-gdbinit script (generated by mk-gdbinit.rkt) gives the type when using
pso, even when the default template did not include the type.

It defaults to printing out only the name of the type without additional
information.
meta/pkg-build/main: fix salvage in case of different versions