Check for broken links and any <a> tags in source code

[delphidabbler]

There are two kinds of problematic links:

1. Broken links
2. Clickable links in source code

• [x] Fix broken links
• [x] Delete clickable links in source code

[delphidabbler]

No broken links found.

• Deleted clickable link in source code in tip 127 (commit 28e4097)
• Updated delphidabbler.com URL in comments in demo 58 Unit1.pas (commit b70eee0)