scripts/functions: cvs retrieval first tries the mirror for tarballs

The cvs download helper looks for the local tarballs dir to see if it
can find a pre-downloaded tarball, and if it does not find it, does
the actual fetch to upstream via cvs.

In the process, it does not even try to get a tarball from the local
mirror, which can be useful if the mirror has been pre-populated
manually (or with a previously downloaded tree).

Fake a tarball get with the standard tarball-download helper, but
without specifying any upstream URL, which makes the helper directly
try the LAN mirror.

Of course, if no mirror is specified, no URL wil be available, and
the standard cvs retrieval will kick in.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@anciens.enib.fr>

timezone data has been split into the package sys-libs/timezone-data

diff -durN glibc-2.13.orig/Makeconfig glibc-2.13/Makeconfig

--- glibc-2.13.orig/Makeconfig	2009-11-13 00:50:13.000000000 +0100

+++ glibc-2.13/Makeconfig	2009-11-13 00:50:41.000000000 +0100

@@ -944,7 +944,7 @@

 	      stdlib stdio-common libio malloc string wcsmbs time dirent    \

 	      grp pwd posix io termios resource misc socket sysvipc gmon    \

 	      gnulib iconv iconvdata wctype manual shadow gshadow po argp   \

-	      crypt nss localedata timezone rt conform debug		    \

+	      crypt nss localedata rt conform debug		    \

 	      $(add-on-subdirs) $(dlfcn) $(binfmt-subdir)

 ifndef avoid-generated