Capitalize/decapitalize only ASCII characters across project

Use {de,}capitalizeAsciiOnly and to{Lower,Upper}CaseAsciiOnly where
possible, and stdlib's functions with Locale.US everywhere else.

Otherwise, if the default system locale is Turkish, the capital latin
letter "I" is transformed in toLowerCase to "ı" (see
https://github.com/JetBrains/kotlin/blob/66bc142f92085047a1ca64f9a291f0496e33dd98/libraries/stdlib/jvm/test/text/StringJVMTest.kt#L119),
which for example breaks the codegen for `intArrayOf` in
KT-25400/KT-43405.

Similarly, lower case latin letter "i" is transformed to "İ".

 #KT-13631 Fixed
 #KT-25400 Fixed
 #KT-43405 Fixed

js/js.dce/src/org/jetbrains/kotlin/js/dce/util.kt

@@ -20,6 +20,7 @@ import org.jetbrains.kotlin.js.backend.ast.*
 import org.jetbrains.kotlin.js.backend.ast.metadata.SpecialFunction
 import org.jetbrains.kotlin.js.backend.ast.metadata.specialFunction
 import org.jetbrains.kotlin.js.dce.Context.Node
+import java.util.*
 
 fun Context.isObjectDefineProperty(function: JsExpression) = isObjectFunction(function, "defineProperty")
 
@@ -46,7 +47,7 @@ fun Context.isObjectFunction(function: JsExpression, functionName: String): Bool
 fun Context.isKotlinFunction(function: JsExpression, name: String): Boolean {
     if (function !is JsNameRef || function.ident != name) return false
     val receiver = (function.qualifier as? JsNameRef)?.name ?: return false
-    return receiver in nodes && receiver.ident.toLowerCase() == "kotlin"
+    return receiver in nodes && receiver.ident.toLowerCase(Locale.US) == "kotlin"
 }
 
 fun isSpecialFunction(expr: JsExpression, specialFunction: SpecialFunction): Boolean =