Fix misc tests on Windows

Completion test used to fail after format_edit_selection test because
teardown of the last one didn't clean up all the data.
Extract teardown_view in format_edit_selection_cmd
Use is_path_absolute() in goto_selected_file()

This partially solves issues with navigation.

Also use copy_str() instead of strcpy().
Use a general function to find the last slash
Merge branch 'handle-backward-slashes-in-menu-item-paths-on-win'

Add handling of paths with backward slashes for :find/:locate/:grep/%M
menus on Windows.

Thanks to Robert Sarkozi.
Use trick with temporary files for timestamps

This prevents rebuilding of all test on each test run.
Combine directory creation targets in Makefile.inc
Merge branch 'optimize-test-building'

Do not rebuild unit-tests without need.
Remove help from data/colors/dmilith-*

No need to duplicate it in each theme.
Mention author of sample color schemes
Add two sample color scheme Daniel R.

Thanks to Daniel R., a.k.a. reicheltd.
Note new sample color scheme in the ChangeLog

Thanks to Daniel R., a.k.a. reicheltd.
Merge branch 'update-color-schemes'

Add sample light color scheme.

Thanks to Daniel R., a.k.a. reicheltd.
Fix a typo in the TODO file
Enable more warnings for compiling unit-tests
Remove unused variable in append_selected_files.c
Fix test_r_ill_formed test

Key enumeration was wrong, strange that it worked.
Fix includes in unit tests
Merge branch 'fix-tests-build'

Enabled -Wall for unit-tests (wasn't enabled by mistake).  This made
tests unbuildable because of -Werror switch, hence some of tests were
updated to fix new warnings.
Make line_completion() testable

I think this is a revert of some previous change made by mistake.