A base for unicode functions, not intended to be a user api.

Whitespace returns a reasonable subset of non nobreak whitespace
characters.

Implementation notes:

Make function clauses instead of using arrays and store tuples instead
of maps to save space.

Add math:floor/1 and math:ceil/1 to avoid unnecessary conversions
in floating point expressions. That is, instead of having to write
float(floor(X)) as part of a floating point expressions, we can
write simply math:floor(X).

* raimo/new-gen-state-machine/OTP-13065: (52 commits)
  Add section on state filtering
  Promote gen_statem over gen_fsm
  Modify code_change/4 to return CallbackMode
  Use ?NAME macro in examples
  Introduce Fred Herbert suggested additions
  Introduce corrections from Fred Hebert and Ingela
  Use .png pictures instead of .gif
  Write Design Principles chapter
  Fix missing short forms for event timeout
  Do more intricate Fred Hebert doc changes
  Change Caller -> From as suggested by Fred Hebert
  Do documentation improvements from Fred Hebert
  Fix broken documenation reference
  Rename state_timeout -> event_timeout
  Fix most of the system docs and emacs mode
  Change code_change/4 to {ok,State,Data}
  Fixup sharpened test suite
  Sharpen test suite
  Remove the remove_event action and all alike
  Relax caller() type check and cleanup
  ...

Conflicts:
	lib/stdlib/src/gen.erl
	lib/stdlib/src/gen_event.erl
	lib/stdlib/src/gen_fsm.erl
	lib/stdlib/src/gen_server.erl
	lib/stdlib/test/error_logger_forwarder.erl

Since no test suites includede test_server.hrl, there is no need
to have test_server in the include path or code path.

Several people have requested that the assert macros in EUnit should be
moved out to a separate header file. This patch puts them in
stdlib/include/assert.hrl, which gets included by the eunit.hrl file.
Thus, nothing changes for eunit users, but the asserts can now also be
included separately.

* dgud/stdlib/rand/OTP-12586:
  stdlib: Document and add normal distributed random value function
  stdlib: Add new random functionality/module