Make Array.size() a function instead of a property

Also add a deprecated extension property to help migration. This is done to
unify getting size of arrays and collections

compiler/testData/codegen/box/vararg/kt581.kt

@@ -4,12 +4,9 @@ import java.util.HashSet
 
 fun iarray(vararg a : Int) = a // BUG
 
-fun IntArray.lastIndex() = size - 1
+fun IntArray.lastIndex() = size() - 1
 
 fun box() : String {
-    // Problematic code does not compile
-//    val vals = iarray(789, 678, 567, 456, 345, 234, 123, 012)
-
     val vals = iarray(789, 678, 567, 456, 345, 234, 123, 12)
     val diffs = HashSet<Int>()
     for (i in vals.indices)