non-portable construct in gcc configure script

[Joe Buck]

In the test labeled

AC_MSG_CHECKING(linker read-only and read-write section mixing)

gcc/configure.in in 3.3 uses "grep -A1".  This feature is not in Solaris's
grep.  It's not in the HP-UX grep either.

The result is that the configure output looks like


checking linker read-only and read-write section mixing... grep: illegal option -- A
grep: illegal option -- 1
Usage: grep -hblcnsviw pattern file . . .

on Solaris 2.8.  The failure appears harmless, but I'm not sure.