i18n: Skips ~h `format' tests when digit grouping info is missing.

* test-suite/tests/i18n.test ("format ~h"): Skip tests when
  `locale-digit-grouping' returns '().
Fix --enable-debug-malloc

* libguile/gc-malloc.c (do_realloc, do_calloc, do_gc_malloc)
  (do_gc_malloc_atomic, do_gc_realloc, do_gc_free): Wrap the allocators
  in helper methods.  The non-GC allocators call
  scm_gc_register_allocation, and the GC allocators ensure that
  gc_malloc returns a nonzero value.
  (scm_realloc, scm_calloc): Allow NULL return for malloc(0).  It is
  permitted by POSIX.  Don't wrap in a SCM_SYSCALL; the only possible
  errno is ENOMEM.
  (scm_gc_malloc_pointerless, scm_gc_malloc, scm_gc_calloc):
  (scm_gc_realloc, scm_gc_free, scm_gc_strndump): Use the wrappers.
  Don't call the debug-malloc registrations and deregistrations, as it
  is neither mandatory nor advised to call scm_gc_free.  Fixes
  compilation with debug-malloc.
  (scm_must_free): Don't scm_malloc_unregister.
i18: avoid freelocale (NULL)

* libguile/i18n.c (smob_locale_free): Don't freelocale (NULL).
Remove incorrect comment in read.c

* libguile/read.c (scm_read_sharp): Remove incorrect comment that
  claims that scm_read_boolean might return a SRFI-4 vector.
Remove inline and register attributes from read.c

* libguile/read.c: Remove all 'inline' and 'register' attributes.
Add and use maybe_annotate_source helper in read.c

* libguile/read.c (maybe_annotate_source): New static helper function.
  (scm_read_sexp, scm_read_quote, scm_read_syntax): Use
  'maybe_annotate_source'.
Optimize empty substring case of scm_i_substring_copy

* libguile/strings.c (scm_i_substring_copy): When asked to create an
  empty substring, use 'scm_i_make_string' to make use of its
  optimization for empty strings that reuses the global null_stringbuf.
Unoptimize 'read' to return freshly allocated empty strings

* libguile/read.c (scm_read_string): Return a freshly allocated string
  every time, even for empty strings.  The motivation is to allow source
  properties to be added to all strings.  Previously, the shared global
  'scm_nullstr' was returned for empty strings.  Note that empty strings
  still share a common global 'null_stringbuf'.

* test-suite/tests/srfi-13.test (substring/shared): Fix tests to reflect
  the fact that empty string literals are no longer guaranteed to be
  'eq?' to each other.
Add source properties to many more types of data

* libguile/read.c (scm_read_array): New internal helper that
  calls scm_i_read_array and sets its source property if the
  'positions' reader option is set.

  (scm_read_string): Set source properties on strings if the 'positions'
  reader option is set.

  (scm_read_vector, scm_read_srfi4_vector, scm_read_bytevector,
  scm_read_guile_bitvector, scm_read_sharp): Add new arguments for the
  'line' and 'column' of the first character of the datum being read.
  Set source properties if the 'positions' reader option is set.

  (scm_read_expression): Pass 'line' and 'column' to scm_read_sharp.

* doc/ref/api-debug.texi (Source Properties): Update manual.
Support => within case, and improve error messages for cond and case

* module/ice-9/boot-9.scm (cond, case): Reimplement using syntax-case,
  with improved error messages and support for '=>' within 'case' as
  mandated by the R7RS.  Add warnings for duplicate case datums and
  case datums that cannot be meaningfully compared using 'eqv?'.

* module/system/base/message.scm (%warning-types): Add 'bad-case-datum'
  and 'duplicate-case-datum' warning types.

* test-suite/tests/syntax.test (cond, case): Update tests to reflect
  improved error reporting.  Add tests for '=>' within 'case'.

* test-suite/tests/tree-il.test (partial evaluation): Update tests to
  reflect changes in how 'case' is expanded.

* doc/ref/api-control.texi (Conditionals): Document '=>' within 'case'.
more efficient scm_to_utf8_stringn, scm_to_utf32_stringn

* libguile/strings.c (scm_to_utf8_stringn): More efficient
  implementation than calling scm_to_stringn.
  (scm_to_utf32_stringn): Likewise.
more efficient scm_string_to_utf8, scm_string_to_utf32

* libguile/bytevectors.c (scm_string_to_utf8): More efficient
  implementation.
  (scm_string_to_utf32): Likewise.
web server: print backtrace on errors when run in batch mode

* module/web/server.scm (read-client, handle-request, write-client):
  When run in batch mode, give a full backtrace for errors.
web server: do not provide a response body where it is not permitted

* module/web/response.scm (response-must-not-include-body?): New
  function.

* doc/ref/web.texi: Doc the function.

* module/web/server.scm (sanitize-response): Error if we have a body,
  but the response type does not permit a body.  If we are responding to
  a HEAD request, silently drop the body.
Fix manual: scm_foreign_to_bytevector to scm_pointer_to_bytevector

* doc/ref/api-foreign.texi (Void Pointers and Byte Access): Fix outdated
  function name: scm_foreign_to_bytevector to scm_pointer_to_bytevector.
web server: fix spurious warning

* module/web/server.scm (sanitize-response): Quick fix to the
  304-has-no-body sanitizer.
Fix typo in comment in message.scm: 'know' to 'known' warning types

* module/system/base/message.scm (%warning-types): Fix typo.
Fix psyntax bugs that would cause bad source annotations

* module/ice-9/psyntax.scm (rebuild-macro-output): Fix two bugs that
  would cause bogus source properties to be added to vectors and
  macro-introduced syntax objects.  These bugs were masked by the
  limitation that only pairs can be decorated with source properties.
  Due to a typo, each vector in the macro output was decorated using the
  vector itself as its source.  Due to accidental variable capture, each
  syntax-object introduced by the macro had its expression decorated
  with its own wrap-subst.

* module/ice-9/psyntax-pp.scm: Regenerate.
syntax-violation: prefer 'subform' for source info, with 'form' as fallback

* module/ice-9/psyntax.scm (syntax-violation): Look for source
  properties of 'subform' first.  If 'subform' has none, 'form' is used.
  Previously, the source information of 'form' was used unless 'form'
  _itself_ was '#f', in which case 'subform' was used.

* module/ice-9/psyntax-pp.scm: Regenerate.
Relax validation of source property accessors

* libguile/srcprop.c (scm_source_properties, scm_source_property,
  scm_i_has_source_properties): Relax validation to allow _any_ object
  to be queried for source properties.