Add description of GAP 4.9.3 release

[olexandr-konovalov]

Does what the title says. The text will look like this:

2.3 GAP 4.9.3 (September 2018)

2.3-1 Changes in the core GAP system introduced in GAP 4.9.3

Fixed bugs that could lead to break loops:

• Fixed a regression in HighestWeightModule (Reference: HighestWeightModule) caused by changes in sort functions introduced in GAP 4.9 release (Fix HighestWeightModule for Lie algebras in certain cases #2617).

Other fixed bugs and further improvements:

• Fixed a compile time assertion that caused compiler error on some systems (kernel: fix GAP_STATIC_ASSERT fallback code #2691).

2.3-2 New and updated packages since GAP 4.9.2

This release contains updated versions of 17 packages from GAP 4.9.1 distribution. Additionally, it has three new packages:

• The curlInterface package by Christopher Jefferson and Michael Torpey, which provides a simple wrapper around libcurl library (https://curl.haxx.se/) to allow downloading files over http, ftp and https protocols.

• The datastructures package by Markus Pfeiffer, Max Horn, Christopher Jefferson and Steve Linton, which aims at providing standard datastructures, consolidating existing code and improving on it, in particular in view of HPC-GAP.

• The DeepThought package by Nina Wagner and Max Horn, which provides functionality for computations in finitely generated nilpotent groups given by a suitable presentation using Deep Thought polynomials.

[olexandr-konovalov]

Building packages failed because of missing curl library - that should be fixed by #2768, and I will rebase this PR then.

[fingolfin]

Please rebase

[codecov]

Codecov Report

Merging #2767 into master will increase coverage by <.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #2767      +/-   ##
==========================================
+ Coverage   75.87%   75.87%   +<.01%     
==========================================
  Files         481      481              
  Lines      241310   241310              
==========================================
+ Hits       183098   183102       +4     
+ Misses      58212    58208       -4

Impacted Files	Coverage Δ
hpcgap/lib/hpc/stdtasks.g	64.45% <0%> (+1.02%)	⬆️

[olexandr-konovalov]

@fingolfin - rebased, now tests pass.

[olexandr-konovalov]

Do not merge this for now - might happen that TransGrp release by @hulpke will be added too.

[olexandr-konovalov]

Updated to increment the count for updated packages - added new release of TransGrp for the redistribution. Just waiting for a couple of more of Jenkins tests to pass before merging this.