Issue #7716: Under Solaris, don't assume existence of /usr/xpg4/bin/grep in
the configure script but use $GREP instead.  Patch by Fabian Groffen.
diff --git a/configure.in b/configure.in
index bd2d027..f3a7ee9 100644
--- a/configure.in
+++ b/configure.in
@@ -2350,7 +2350,7 @@
 			;;
 		solaris)
 			if test -f /etc/netconfig; then
-                          if /usr/xpg4/bin/grep -q tcp6 /etc/netconfig; then
+                          if $GREP -q tcp6 /etc/netconfig; then
 				ipv6type=$i
 				ipv6trylibc=yes
                           fi