add http mirrors to packages hosted at FTP

see http://lists.nongnu.org/archive/html/mingw-cross-env-list/2014-07/msg00002.html

Many FTP servers block connections from Tor and some
VPN servers. HTTP servers don't do this normally.

Example of failed FTP download attempt of binutils-2.24.tar.bz:

```
$ torsocks wget ftp://ftp.gnu.org/pub/gnu/binutils/binutils-2.24.tar.bz2
   --2014-07-20 13:26:48-- ftp://ftp.gnu.org/pub/gnu/binutils/binutils-2.24.tar.bz2
   => `binutils-2.24.tar.bz2'
   Resolving ftp.gnu.org (ftp.gnu.org)... 208.118.235.20
   Connecting to ftp.gnu.org (ftp.gnu.org)|208.118.235.20|:21... connected.
   Logging in as anonymous ... Logged in!
   ==> SYST ... done.    ==> PWD ... done.
   ==> TYPE I ... done.  ==> CWD (1) /pub/gnu/binutils ... done.
   ==> SIZE binutils-2.24.tar.bz2 ... 22716802
   ==> PASV ... done.    ==> RETR binutils-2.24.tar.bz2 ...
   Error in server response, closing control connection.
   Retrying.
```

Same package was downloaded via HTTP successfully:
```
$ torsocks wget http://ftp.gnu.org/pub/gnu/binutils/binutils-2.24.tar.bz2
    --2014-07-20 13:32:37-- http://ftp.gnu.org/pub/gnu/binutils/binutils-2.24.tar.bz2
    Resolving ftp.gnu.org (ftp.gnu.org)... 208.118.235.20
    Connecting to ftp.gnu.org (ftp.gnu.org)|208.118.235.20|:80... connected.
    HTTP request sent, awaiting response... 200 OK
    Length: 22716802 (22M) [application/x-bzip2]
    Saving to: `binutils-2.24.tar.bz2'

    100%[=================>] 22,716,802   721K/s   in 24s

    2014-07-20 13:33:03 (915 KB/s) - `binutils-2.24.tar.bz2' saved [22716802/22716802]

Trying download from Tor Browser, I get error message:
425 Security: Bad IP connecting.
```

HTTP URLs were added to FTP URLs-only packages.
In many cases, ftp://ftp.gnu.org can be accessed
from http://ftp.gnu.org
If both URLs of a package are FTP, then one of them
was replaced with HTTP.

Command to check that those packages can be build successfully
if behind Tor:
```
$ torsocks make autoconf automake binutils bison cloog coreutils file freetds gcc gdb gettext gmp gnutls gperf isl libbluray libffi libgcrypt libgpg_error libidn libmicrohttpd libpng libxml2 libxslt m4 pthreads-w32 sed dcmtk mpfr
```

I've run the test above successfully.