get GI generation script running and fix argument order in @GType_decl

[jwahlstrand]

In @gtype and @GType_decl, the order of arguments in the call to
get_type_decl() isn't consistent. As far as I can tell, @GType_decl
is not used within Gtk.jl. But it is used in the GObject introspection
code (GI.jl).

modified:   gen/gi_gen_consts.jl
modified:   src/GLib/gtype.jl

Fixes #277 (at least partially)

[codecov]

Codecov Report

Merging #582 (dbfc417) into master (0ff7447) will decrease coverage by 0.43%.
The diff coverage is n/a.

❗ Current head dbfc417 differs from pull request most recent head 6ba7053. Consider uploading reports for the commit 6ba7053 to get more accurate results

@@            Coverage Diff             @@
##           master     #582      +/-   ##
==========================================
- Coverage   48.10%   47.67%   -0.44%     
==========================================
  Files          32       32              
  Lines        2580     2211     -369     
==========================================
- Hits         1241     1054     -187     
+ Misses       1339     1157     -182     

Impacted Files	Coverage Δ
src/GLib/gtype.jl	76.07% <ø> (+0.44%)	⬆️
src/GLib/gerror.jl	33.33% <0.00%> (-16.67%)	⬇️
src/theme.jl	35.71% <0.00%> (-9.29%)	⬇️
src/displays.jl	9.52% <0.00%> (-3.96%)	⬇️
src/GLib/MutableTypes.jl	59.09% <0.00%> (-3.41%)	⬇️
src/toolbar.jl	75.00% <0.00%> (-2.78%)	⬇️
src/GLib/GLib.jl	70.00% <0.00%> (-2.73%)	⬇️
src/selectors.jl	20.65% <0.00%> (-1.99%)	⬇️
src/GLib/glist.jl	15.71% <0.00%> (-1.66%)	⬇️
src/lists.jl	56.22% <0.00%> (-1.64%)	⬇️
... and 19 more

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