stdlib/lists: Add function droplast/1
This functions drops the last element of a non-empty list.

lists:last/1 and lists:droplast/1 are the dual of hd/1 and tl/1 but
for the end of a list.
Added tests for lists:droplast/1 to stdlib/lists_SUITE
Added documentation of lists:droplast/1
Import and use lists:droplast/1 in v3_core/v3_kernel

Also imported lists:last/1, and removed the local definition.
Use lists:droplast/1 in orber/orber_interceptors.erl
lib/wx - Replace reverse(tl(reverse(L))) with lists:droplast/1
lib/ssh - Replace reverse(tl(reverse(L))) with lists:droplast/1
Issue a warning when a named fun is constructed but not used
Add a spec for a function that does not return
Shut off a dialyzer unmatched return warning

Dialyzer does not like list comprehensions for which the result is not
assigned to some variable (maybe anonymous).  In this particular case,
the comprehension, containing only a filter but no generator, was used
to save some lines, but IMO this type of code, while "cute", is not so
easy to comprehend.
compiler: Strengthen Maps tests
compiler: Strengthen listings tests
compiler: Fold binary Map key patterns to literals
compiler: Teach beam_disasm has_map_field instruction
Document maps-related abstract syntax trees

	{map,Loc,Fields}
	{map,Loc,Argument,Fields}

	{map_field_assoc,Loc,Name,Value}
	{map_field_exact,Loc,Name,Value}
Complete support of maps in erl_syntax

	map_expr/1
	map_expr/2
	map_expr_argument/1
	map_expr_fields/1

	map_field_assoc/2
	map_field_assoc_name/1
	map_field_assoc_value/1

	map_field_exact/2
	map_field_exact_name/1
	map_field_exact_value/1
Support named funs in erl_prettypr
Support maps in erl_prettypr
Don't munge record and field names in cover

They are bare atoms, atoms or variables in the abstract format, there is no need to
pass them through munge_expr/2.
Properly munge record updates in cover

Trees {record,Line,Arg,Name,Fields} were not munged.