gen_abi.sh: filter out symbols not needed for ABI

gdb does not allow to print definitions of certain section names
and special symbols used for dynamic loading machinery:

__bss_start
_edata
_init
_fini
_end

Please note the space before the pattern, it is needed to avoid
hungry matches of valid symbols with these as substrings (foo_init,
for example).

Without this patch gdb on Fedora 18 breaks when attempting to print
function and struct signature.

buildtools/scripts/abi_gen.sh

@@ -10,7 +10,7 @@ cat <<EOF
 set height 0
 set width 0
 EOF
-nm "$SHAREDLIB" | cut -d' ' -f2- | egrep '^[BDGTRVWS]' | grep -v @ | cut -c3- | sort | while read s; do
+nm "$SHAREDLIB" | cut -d' ' -f2- | egrep '^[BDGTRVWS]' | grep -v @ | egrep -v ' (__bss_start|_edata|_init|_fini|_end)' | cut -c3- | sort | while read s; do
     echo "echo $s: "
     echo p $s
 done