configure: correct the wording when checking grep -E

The check first checks that grep -E works, and only as a fallback tries
to find and use egrep. egrep is deprecated.

This change only corrects the output wording, not the checks themselves.

Closes #9471

configure.ac

@@ -85,21 +85,22 @@ if test -z "$GREP"; then
 fi
 AC_SUBST([GREP])
 
-dnl EGREP is mandatory for configure process and libtool.
+dnl 'grep -E' is mandatory for configure process and libtool.
 dnl Set it now, allowing it to be changed later.
 if test -z "$EGREP"; then
   dnl allow it to be overridden
+  AC_MSG_CHECKING([that grep -E works])
   if echo a | ($GREP -E '(a|b)') >/dev/null 2>&1; then
-    AC_MSG_CHECKING([for egrep])
     EGREP="$GREP -E"
-    AC_MSG_RESULT([$EGREP])
+    AC_MSG_RESULT([yes])
   else
+    AC_MSG_RESULT([no])
     AC_PATH_PROG([EGREP], [egrep], [not_found],
       [$PATH:/usr/bin:/usr/local/bin])
   fi
 fi
 if test -z "$EGREP" || test "$EGREP" = "not_found"; then
-  AC_MSG_ERROR([egrep not found in PATH. Cannot continue without egrep.])
+  AC_MSG_ERROR([grep -E is not working and is egrep not found in PATH. Cannot continue.])
 fi
 AC_SUBST([EGREP])