[test_server] Use simpler tc name in unicode test to make it work on windows

A test case in test_server_unicode_SUITE contained characters that
were not allowed in filenames on windows - e.g. \. The test case name
will be used as filename for the HTML log for the test, so this failed
on windows. This is now corrected.
[test_server] Fix encoding of HTML file references to work on windows

The URI encoding when in unicode  file name mode did not preserve @, :
and  /, and  thus  some links  were  did not  work  on windows  (think
c:/). This has been corrected.
[test_server] Clean up unused code in test_server_SUITE
[test_server] Remove unused code related to remote targets

After removing the functionality for remote target nodes in R16A,
there was still some unused code left and some documentation that was
not updated. This is now completed.
Checking if jinterface is present
String instead of atom, not_found handled by ts:make
Merge branch 'fredrik/ic_make_ji/OTP-10876' into maint

* fredrik/ic_make_ji/OTP-10876:
  String instead of atom, not_found handled by ts:make
  Checking if jinterface is present
Merge branch 'siri/cuddle-with-tests' into maint

* siri/cuddle-with-tests:
  [sasl] Fix tests that compare execution time
  [jinterface] Kill process between tests to avoid consequential error
  [jinterface] Make tests handle space in path on windows
  [common_test] Extend timers for slave nodes in ct_cover_SUITE
  [test_server] Clean up unused code in test_server_SUITE
  [reltool] Increase timetrap timeout for reltool_server_SUTIE to 10 minutes
  [test_server] Fix encoding of HTML file references to work on windows
  [test_server] Use simpler tc name in unicode test to make it work on windows
[test_server] Don't hang due to invalid io request

A bug in test_server_gl caused io requests containing invalid data
(i.e. not unicode:chardata()) to hang, since no io reply was
sent. This has been corrected.
[test_server] Quote path to erl executable when starting slave nodes

This is to allow space in path.
[test_server] Add test_server_io:print_unexpected/1

To use from any process to print a string in the unexpected_io.log.
Encode Erlang source files with non-ascii characters in UTF-8

To ensure that 'master' compiles when we merge 'maint' to it,
regardless of which encoding is default in 'master', all source
files with non-ascii characters *must* have the encoding specified.
Make test_server close log files properly and include correct footer

OTP-11046
Remove the "coding: utf-8" comment from all Erlang source files
Convert XML files to UTF-8
Merge branch 'maint'
Add long_schedule detection for ports and testcases
Prepare release
Merge branch 'maint-r15' into maint-r16
Merge branch 'maint-r16' into maint