Update libchdr to upstream

[lgtm-com[bot]]

This pull request introduces 6 alerts and fixes 4 when merging cad67d2bdb4c937f9059638881f3ae9804b2d5ce into 9e87be6f57f8e321e701b0a8eb24937721dc18d6 - view on LGTM.com

new alerts:

• 3 for Missing header guard
• 2 for Implicit function declaration
• 1 for Multiplication result converted to larger type

fixed alerts:

• 3 for Missing header guard
• 1 for Multiplication result converted to larger type