When printing function, reproduce TryNextMethod() correctly

[fingolfin]

Before:

gap> Display(function() TryNextMethod(); end);
function (  )
    return TRY_NEXT_METHOD;
end

After:

gap> Display(function() TryNextMethod(); end);
function (  )
    TryNextMethod();
end

[codecov]

Codecov Report

Merging #1613 into master will increase coverage by 14.48%.
The diff coverage is 100%.

@@             Coverage Diff             @@
##           master    #1613       +/-   ##
===========================================
+ Coverage   49.52%   64.01%   +14.48%     
===========================================
  Files         456      998      +542     
  Lines      238345   327608    +89263     
  Branches    10654    13215     +2561     
===========================================
+ Hits       118044   209706    +91662     
+ Misses     117487   115045     -2442     
- Partials     2814     2857       +43

Impacted Files	Coverage Δ
src/c_oper1.c	87.45% <ø> (+1.49%)	⬆️
hpcgap/src/c_oper1.c	86.18% <ø> (ø)
src/stats.c	73.2% <100%> (+1.9%)	⬆️
src/funcs.c	72.35% <0%> (-14.44%)	⬇️
src/blister.h	92% <0%> (-8%)	⬇️
src/objects.h	80% <0%> (-5.19%)	⬇️
src/plist.h	92.98% <0%> (-1.31%)	⬇️
src/dteval.c	2.79% <0%> (-0.29%)	⬇️
src/dt.c	1.61% <0%> (-0.26%)	⬇️
hpcgap/pkg/gapdoc/lib/GAPDoc2Text.gi	0.46% <0%> (-0.15%)	⬇️
... and 876 more