Rida: Parsing of .plt.sec section added for x86/64 ubuntu 20 needed to be
updated to support x86/32 in ubuntu 20.

Fix-calls: Thunk checks aged poorly.  Revived/fixed some of them.

Shared libs need a reloc for a code pointer to live in rodata.
I found in ffmpeg that many spurious pins were occuring because constant
(particularly with relatively small values) data looked like code poitners
(because the code's load point is address 0 in a shared library).

To avoid these spuriosu pins, I extended the code pin algorithm
to check isDLL() (which includes shared objects) and for a reloc
before attempting to pin in the rodata.

A perf. optimization verifies that it _might_ result in a pin
before checking for a reloc, as checking for a reloc can be slow,
while checking for a possible pin location is fast.

Table size min was set to <=4 items, but readelf on ubuntu20
had a switch table with exactly 4 elements.  This caused
FII to miss the table size and subsequently include _many_ extra IBTs.
Ultimately, Zipr failed by trying to 68-sled an entire function due to
FII's failure.

Enhancement: Make rida support enhanced PLTs

See merge request !11

Starting in new(er) versions of Ubuntu distros, PLT entries use
the bnd prefix to make sure that jump targets are in bounds. This
patch adds conditional support for those PLT styles.