patchset v2: remove remaining internal uses of AC_EGREP_{CPP,HEADER}

[Zack Weinberg]

This patchset removes all remaining internal uses of AC_EGREP_CPP and
AC_EGREP_HEADER.  (See the bottom of
https://www.gnu.org/savannah-checkouts/gnu/autoconf/manual/autoconf-2.71/html_node/Running-the-Preprocessor.html
for why this is desirable.)

Many of the modified tests are obsolete in some way and I tried to push
them farther down the road to removal, while also striving not to break
existing configure scripts.

See individual patches for notes.  Testing would be appreciated,
especially on older and weirder OSes; the complete patchset is available
from the 'zack/no-internal-egrep-cpp' branch on savannah
<https://git.savannah.gnu.org/cgit/autoconf.git/log/?h=zack/no-internal-egrep-cpp>
.

zw

0003-Fold-AC_C_STRINGIZE-into-AC_PROG_CC.patch
Description: Text Data

0002-Overhaul-AC_TYPE_GETGROUPS-and-AC_FUNC_GETGROUPS.patch
Description: Text Data

0001-Make-AC_PROG_GCC_TRADITIONAL-a-compatibility-alias-f.patch
Description: Text Data

0004-Remove-the-last-few-internal-uses-of-AC_EGREP_CPP.patch
Description: Text Data