This patch implements ld.so code that makes use of both .init_array and
.fini_array. .init_array is fully utilized and is used in the correct
manner. However .fini_array is not used yet although the function that
runs .fini_array exists

This patch implements tree-based data-structure for catching circular
dependency where libA.so will depen on arbitrarily long chain (including
zero length) of libNs.so one of which will depend on libA.so again. The
main intention of this patch was merely capturing the dependency tree to
prioterize which Elf's .init_array and which .fini_array should run
first, but as a side effect it can capture circular dependencies as well.

This patch makes use of the data structures and functions impelemented
in the last patch to enable RTLD debugging protocol as per SVR4

At least in linux kernel, assuming that a.out is an elf that is linked
against relibc's own ld.so. When a user attempts `./a.out`, Linux kernel
will map `./a.out`, then map `ld.so` and jump into ld.so entry point.
In relibc ld.so will simply ignore the kernel mapped a.out and create
its own mapping. This patch forces relic ld.so to use the already mapped
`a.out` when ever possible. This would normally have slight performance
improvement (especially that currently relibc doesn't map a.out but
instead copy the data into empty mmaped memory).

The real motivation behind this patch is while impelemnting Runtime
linker debugging protocol for relibc. part of the protocol is ld.so
inseting address of some ld.so managed data structure into .dynamic
seciton of a.out then the debugger would check it there. The thing is
that debuggers have information about the kernel loaded ./a.out and they
check that one specifically which is in our case totally ignored by
relibc.

This patch keep 2 lists, one for strong symbols and one for weak
symbols. First it will check for the symbol to be resolved in the strong
symbols' list, if it is not there it will then check in the weak symbol
list.

This patch does basically two things:
- First make `global` variable not public, And make it accessable via a
function `get_sym`.
- Isolate the procedure that collect global symbols into single function
that does that and call it `collect_syms`.

The motivation of this patch is the second one where this procedure is
extended, thus it needs a seamless way to access those symbols

I didn't think it'd be this useful first, but thank god for `cargo fix --edition`!

Just a small step along the way to reduce the massive wall of spam
every time you compile.

This was done partly automagically with `cargo fix`. The rest was me
deleting or commenting out a bunch of variables. Hope nothing was
important...