Apply automatic code fixes for php 7.2 target

[glensc]

• Apply void_return fixer
• Apply visibility_required fixer
• Apply list_syntax fixer

[glensc]

@markstory stickler-ci Failing again and the link points to URL that I can not access:

• https://stickler-ci.com/repositories/156-perftools-xhgui

[glensc]

@markstory stickler-ci Failing again and the link points to URL that I can not access:

• stickler-ci.com/repositories/156-perftools-xhgui

Update: The errors can be seen from Checks tab:

• https://github.com/perftools/xhgui/pull/400/checks