doc updates for section "Particular Functions"

[Bruno Haible]

Hi,

Paul's commit yesterday
<https://lists.gnu.org/archive/html/bug-gnulib/2020-07/msg00192.html>
reminded me that Autoconf contains some macros that have more complete
and up-to-date counterparts in Gnulib.

Here are three proposed patches, all to the documentation section "Particular
Functions".

- 0001 ensures that for every Autoconf macro that possibly does an AC_LIBOBJ
  invocation, we point to Gnulib. So that the user does not have to provide
  and maintain their own copy of malloc.c, obstack.c, etc.

- 0002 adds references to Gnulib also for other macros, where Gnulib has
  significant workarounds.

- 0003 updates the documentation also for macros for which no corresponding
  Gnulib module exists.

Bruno

0001-doc-Refer-to-Gnulib-instead-of-asking-clients-to-pro.patch
Description: Text Data

0002-doc-Refer-to-Gnulib-where-it-makes-sense.patch
Description: Text Data

0003-doc-Update-some-more-macro-descriptions.patch
Description: Text Data