Update build_style for all templates.

- There's no need to set build_style for custom-install (default).
- gnu_{configure,makefile} renamed to gnu-{configure,makefile}.

srcpkgs/db/template

@@ -4,7 +4,7 @@ version=4.8.26
 revision=1
 wrksrc="db-${version}"
 distfiles="http://download-uk.oracle.com/berkeley-db/db-${version}.tar.gz"
-build_style=gnu_configure
+build_style=gnu-configure
 build_wrksrc="build_unix"
 configure_script="../dist/configure"
 configure_args="--enable-compat185 --enable-cxx --enable-o_direct