The test case did not test the log files were created. And they
were not created, because filelib:ensure_dir/1 was used
incorrectly.

Include the ability to open a SASL error log file in append mode
at startup vs currently implemented "rewrite-always" mode.

release_handler_SUITE:otp_10463_upgrade_script_regexp reads
kernel.appup and tries to fetch upgrade instructions for upgrade from
current version to current version. The point of the test is to see
that release_handler can read an appup with regexps.

In some cases, however, kernel.appup does not support upgrade from
current to current version, since this is not necessary in real
life. Therefore this test is now updated to use a dummy application
(release_handler_SUITE_data/regexp_appup/app1) for this test.

The upgrade instruction 'remove_module' was added in OTP R7B (and
possibly in a patch in R5B or R6B, ticket OTP-3477), and translates to
the low level instruction 'remove', but adds the parameter DepMods
(modules on which Mod is dependent). The ticket says that
"remove_module should be added for symmetry with the add_module
instruction". remove_module was never documented or tested, and it was
never mentioned in a release note. It therefore seems to be low risk
in removing it.

The correct instruction to use when removing a module is

{delete_module,Mod}

which was added in OTP R10B and which is also documented and
tested. This translates to low level instructions 'remove' and 'purge'
i.e. the module is brutally purged after setting the current code to
old. This hardcoded brutal purge is the reason why PrePurge and
PostPurge parameters can not be given with the delete_module
instruction.

The parameter DepMods which was inclued in the remove_module
instruction does not exist for delete_module. From the documentation's
point of view, this is the same for add_module, and thus the two
instructions {add_module,Mod} and {delete_module,Mod} are now
symmetric. However, in the code there is a second instruction for
adding a module, {add_module,Mod,DepMods}, which is not documented. To
add symmetry even for this, {delete_module,Mod,DepMods} is now also
added. Documentation is added for all instructions.

The appup tests for kernel, stdlib and sasl tests that the appup file
allows upgrade from the previous and current major release to the
current release. If, in the current release, the application version
was not changed compared to the previous release, then we would still
test that the appup supported the upgrade (i.e. from current release
to current release). This is now changed, in order to avoid test
failures on patch releases where kernel, stdlib and sasl are not
changed.