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/nasm.tmpl

@@ -2,7 +2,7 @@
 pkgname=nasm
 version=2.05
 distfiles="
-http://www.nasm.us/pub/nasm/releasebuilds/$version/$pkgname-$version@.tar.bz2"
+http://www.nasm.us/pub/nasm/releasebuilds/$version/$pkgname-$version.tar.bz2"
 build_style=gnu_configure
 short_desc="The Netwide Assembler"
 maintainer="Juan RP <xtraeme@gmail.com>"