Ignore Fractional Part of Drawing Shadow Alpha

[oleibman]

Fix #4415. We store the rarely-used property Drawing/Shadow/Alpha as an integer representing the percentage. Excel also stores it as an integer, but multiplies it by 1,000, so we divide by 1,000 when we read this value. This can, and in the case of the issue at hand does, leave a fractional portion. Php has deprecated passing a float with a fractional portion to an int argument, so the reporter saw a deprecation message. This is easily fixed.

This is:

• a bugfix
• a new feature
• refactoring
• additional unit tests

Checklist:

• Changes are covered by unit tests
  • Changes are covered by existing unit tests
  • New unit tests have been added
• Code style is respected
• Commit message explains why the change is made (see https://github.com/erlang/otp/wiki/Writing-good-commit-messages)
• CHANGELOG.md contains a short summary of the change and a link to the pull request if applicable
• Documentation is updated as necessary