[GSOC]Dynamic object file loading:basic working version

[JiSheng Zhang]

Hi all,
Now basic symbol resolving and relocation works! The code is attached.
For test just make and then ./demo -l ./t.o -s get. If you should see
something like "******5******" plus various debug message.
Explanation:
t.c looks like this:
/*****************/
int ttt=5;
int get()
{
       return ttt;

}
/****************/
so t.o should have at least one relocation and two symbols. readelf -S
t.o and readelf -s t.o prove this.
the dynamic linker load t.o and parsing it, then it loading all needed
sections, finally it will do symbol resolving and relocation.

For test I just point entry to the start of ".text" that is get
function, then call this  function via entry, we should get the
result:5

TODO next week:
1.lookup external symbol which is exported by demo
2.support symbol resolving exported by object file which is dynamic loaded

Regards,
JiSheng
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