Improve support for S390 architecture

[fanquake]

Cross-compile a minimal test.cpp using s390x-linux-gnu-g++:

#include <iostream>
int main(void) {
        std::cout << "Hello s390x!\n";
        return 0;
}

s390x-linux-gnu-g++ test.cpp

import lief

binary = lief.parse("a.out")
print(binary)

Architecture S390 not implemented
Architecture S390 not implemented
Architecture S390 not implemented
Architecture S390 not implemented
Architecture S390 not implemented
Architecture S390 not implemented
Header
======
Magic:                           7f 45 4c 46 
Class:                           CLASS64
Endianness:                      MSB
Version:                         CURRENT
OS/ABI:                          SYSTEMV
ABI Version:                     0
Machine type:                    S390
File type:                       DYNAMIC

or

import lief

binary = lief.parse("a.out")
print(binary.abstract.header.architecture)

S390 is not supported!
ARCHITECTURES.NONE

[romainthomas]

Ack