pppd: fix build with glibc 2.28

pppd: fix build with glibc 2.28

Since glibc 2.28
(https://savannah.gnu.org/forum/forum.php?forum_id=9205), the obsolete
functions encrypt, encrypt_r, setkey, setkey_r, cbc_crypt, ecb_crypt,
and des_setparity are no longer available to newly linked binaries, and
the headers <rpc/des_crypt.h> and <rpc/rpc_des.h> are no longer
installed. These functions encrypted and decrypted data with the DES
block cipher, which is no longer considered secure. Software that still
uses these functions should switch to a modern cryptography library,
such as libgcrypt.

So retrieve an upstream patch to use openssl instead of these functions
and a new patch to remove the unsafe header/library path
'-I/usr/include/openssl'

Fixes:
 - http://autobuild.buildroot.org/results/c13ca8b8afa8de700caf8cd2fa1812b8552b3f4a

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>