We inadventently wrote out 'coerce' casts in .opt files as:
V_2 = 'coerce expression'(V_3).
In commit 233874403f, cast_type_to_string
was changed to return "coerce expression" instead of simply "coerce"
for a slight improvement in mode errors.
compiler/hlds_out_goal.m:
Don't use the result of cast_type_to_string when when writing out
coerce casts.
tests/hard_coded/Mercury.options:
tests/hard_coded/Mmakefile:
tests/hard_coded/coerce_opt.exp:
tests/hard_coded/coerce_opt.m:
tests/hard_coded/coerce_opt_2.m:
Add test case.
