csso mis-compression of escape sequence in v5.0.0+ #452

Starting from csso 5.0.0 (including the latest 5.0.3), it has similar issue as this example:

Original css: .star-rating{content:'\73\73\73\73\73'} .star-rating span::before{content:'\53\53\53\53\53'}

After csso minification: .star-rating{content:"sssss"}.star-rating span::before{content:"SSSSS"}

V4.2.0 does not have this issue, it will just keep the original value.

Please kindly look into this and fix it as needed.

Thanks