Should support overlapping instructions

[rfalke]

Background: https://reverseengineering.stackexchange.com/questions/1531/what-is-overlapping-instructions-obfuscation

Subject: https://github.com/rfalke/decompiler-subjects/blob/master/from_holdec/overlapping_instructions/ia32_elf/subject.exe

In this subject the method add_one() is the most basic case. But reko detects wrongly void as return type.

Another method is return_constant() which reko decompiles as:

void return_constant()
{
    while (true)
        ;
}

but should be a simple ...{ return -1163082564;} or ... {return 0xbaacc4bc;}.

[rfalke]

Still relevant in 0.11.4.0-931ca7d.