Number: Remove unused code, fix strict mode

Comments from rxaviers:

The variable name `negativeSuffix` was a typo. It should have been 
`negativeProperties`. Although, it also doesn't make sense to set
`negativeProperties` at all. This variable is only used as an auxiliary
variable to get `negativePrefix` and `negativeSuffix`. Therefore, I 
believe that's was mistake when compact support was implemented. That
mistake doesn't cause any bug, because this variable isn't used and it's 
ignored.

src/number/format-properties.js

@@ -71,11 +71,11 @@ return function( pattern, cldr, options ) {
 		// the value to be formatted, though we're always using 1 as a simplification, because the
 		// number won't be zero-padded since we chose the right format based on the scale, i.e.,
 		// we'd never see something like `003M` anyway.
-		properties[ 2 ] = negativeSuffix[ 2 ] = 1; // minimumIntegerDigits
-		properties[ 3 ] = negativeSuffix[ 3 ] = 0; // minimumFractionDigits
-		properties[ 4 ] = negativeSuffix[ 4 ] = 0; // maximumFractionDigits
-		properties[ 5 ] = negativeSuffix[ 5 ] = // minimumSignificantDigits &
-			properties[ 6 ] = negativeSuffix[ 6 ] = undefined ; // maximumSignificantDigits
+		properties[ 2 ] = 1; // minimumIntegerDigits
+		properties[ 3 ] = 0; // minimumFractionDigits
+		properties[ 4 ] = 0; // maximumFractionDigits
+		properties[ 5 ] = // minimumSignificantDigits &
+			properties[ 6 ] = undefined ; // maximumSignificantDigits
 
 		properties[20] = numberCompact( options.compact, cldr );
 	}