[FFmpeg-cvslog] configure: Avoid use of nonstandard features of sed

[Mark Thompson]

ffmpeg | branch: master | Mark Thompson <sw at jkqxz.net> | Sun Dec  2 23:31:50 2018 +0000| [2f6b1806ce2bc007a3a3596680a9f8089fb78145] | committer: Mark Thompson

configure: Avoid use of nonstandard features of sed

Standard sed does not support EREs.

Fixes #7310.

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=2f6b1806ce2bc007a3a3596680a9f8089fb78145
---

 configure | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/configure b/configure
index 2af6c0d797..ed77b4ee81 100755
--- a/configure
+++ b/configure
@@ -3725,8 +3725,7 @@ find_things_extern(){
 
 find_filters_extern(){
     file=$source_path/$1
-    #sed -n "s/^extern AVFilter ff_\([avfsinkrc]\{2,5\}\)_\(\w\+\);/\2_filter/p" $file
-    sed -E -n "s/^extern AVFilter ff_([avfsinkrc]{2,5})_([a-zA-Z0-9_]+);/\2_filter/p" $file
+    sed -n 's/^extern AVFilter ff_[avfsinkrc]\{2,5\}_\([[:alnum:]_]\{1,\}\);/\1_filter/p' $file
 }
 
 FILTER_LIST=$(find_filters_extern libavfilter/allfilters.c)