Ignore __bss_start, _edata and _end symbols.

This is equivalent to glib commit 936ff022f21a43f39552799dc1b3988379563959:
  https://mail.gnome.org/archives/commits-list/2010-May/msg03273.html

diff -x config.log -x config.status -ru tmp/harfbuzz-0.9.4/src/check-exported-symbols.sh work/harfbuzz-0.9.4/src/check-exported-symbols.sh
--- tmp/harfbuzz-0.9.4/src/check-exported-symbols.sh	2012-08-08 23:03:22.000000000 +0100
+++ work/harfbuzz-0.9.4/src/check-exported-symbols.sh	2012-11-27 22:28:25.826000303 +0000
@@ -24,7 +24,7 @@
 		echo "Checking that $so has the same symbol list as $def"
 		{
 			echo EXPORTS
-			nm "$so" | grep ' [BCDGINRSTVW] ' | grep -v ' T _fini\>\| T _init\>' | cut -d' ' -f3
+			nm "$so" | grep ' [BCDGINRSTVW] ' | grep -v ' T _fini\>\| T _init\>\| __bss_start\>\| _edata\>\| _end\>' | cut -d' ' -f3
 			stat=1
 			# cheat: copy the last line from the def file!
 			tail -n1 "$def"
diff -x config.log -x config.status -ru tmp/harfbuzz-0.9.4/src/check-internal-symbols.sh work/harfbuzz-0.9.4/src/check-internal-symbols.sh
--- tmp/harfbuzz-0.9.4/src/check-internal-symbols.sh	2012-08-08 23:02:54.000000000 +0100
+++ work/harfbuzz-0.9.4/src/check-internal-symbols.sh	2012-11-27 22:27:53.240000303 +0000
@@ -19,7 +19,7 @@
 	so=`echo .libs/libharfbuzz$suffix`
 	if test -f "$so"; then
 		echo "Checking that we are not exposing internal symbols"
-		if nm "$so" | grep ' [BCDGINRSTVW] ' | grep -v ' T _fini\>\| T _init\>\| T hb_'; then
+		if nm "$so" | grep ' [BCDGINRSTVW] ' | grep -v ' T _fini\>\| T _init\>\| T hb_\| __bss_start\>\| _edata\>\| _end\>'; then
 			echo "Ouch, internal symbols exposed"
 			stat=1
 		fi