Make it possible to generate GAP functions from Julia

[sebasguts]

No description provided.

[sebasguts]

This allows for:

               _
   _       _ _(_)_     |  Documentation: https://docs.julialang.org
  (_)     | (_) (_)    |
   _ _   _| |_  __ _   |  Type "?" for help, "]?" for Pkg help.
  | | | | | | |/ _` |  |
  | | |_| | | | (_| |  |  Version 1.1.0 (2019-01-21)
 _/ |\__'_|_|_|\__'_|  |  Official https://julialang.org/ release
|__/                   |

julia> using GAP
Adding path /home/sebastian/Software/GAPJulia/gap/.libs to DL_LOAD_PATH
 ┌───────┐   GAP 4.dev of today
 │  GAP  │   https://www.gap-system.org
 └───────┘   Architecture: x86_64-pc-linux-gnu-julia64-kv6
 Configuration:  gmp 6.1.2, Julia GC, Julia 1.1.0, readline
 Loading the library and packages ...
^[[B Packages:   GAPDoc 1.6.1, PrimGrp 3.3.1, SmallGrp 1.3, TransGrp 2.0.4
 Try '??help' for help. See also '?copyright', '?cite' and '?authors'

julia> oper = (i,g)->i^g
#3 (generic function with 1 method)

julia> GAP.Globals.Orbit(GAP.Globals.SymmetricGroup(3),1,GAP.julia_to_gap(oper))
GAP: [ 1, 2, 3 ]

[codecov]

Codecov Report

Merging #212 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #212   +/-   ##
=======================================
  Coverage   91.31%   91.31%           
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  Files          25       25           
  Lines        1486     1486           
=======================================
  Hits         1357     1357           
  Misses        129      129

[fingolfin]

Please rebase so that CI runs again and we get proper coverage.

[sebasguts]

Done.

[fingolfin]

Clearly something is still broken wrt coverage, the C code has no coverzreported (and hence this PR shows no coverage).

[fingolfin]

Am on a phone only now, but: do we still oasd --coverage in CFLAGS and LDFLAGS when compiling our code? (Possibly indirectly, if GAP was compiled with those flags)

[sebasguts]

@fingolfin We don't for the GAP compiled by julia, I assume. Should I add this simply to the debug mode? Guess it won't hurt there.

[fingolfin]

While we don't get proper coverage return now, it is clear there there is a test case here, so all should be fine (and if not, we can revisit it later).
I'd perhaps insert one space after a comma, but other than that, let's just merge this.