Use bash features to improve $distfiles parsing.

That means that it's not necessary anymore to use an '@' before the
extract suffix string. yay.

--HG--
extra : convert_revision : 83ce2c783cb917ef59b87eacb0565cfcff277218

templates/flex.tmpl

@@ -1,7 +1,7 @@
 # Template file for 'flex'
 pkgname=flex
 version=2.5.35
-distfiles="http://prdownloads.sourceforge.net/flex/$pkgname-$version@.tar.bz2"
+distfiles="http://prdownloads.sourceforge.net/flex/$pkgname-$version.tar.bz2"
 build_style=gnu_configure
 configure_args="--disable-rpath"
 short_desc="The Fast Lexical Analyzer"