JS backend: don't use octal numbers when render non-latin symbols, because of it prohibited in strict mode

#KT-7921 Fixed

js/js.translator/testData/char/cases/charConstantByUnicodeId.kt

@@ -0,0 +1,20 @@
+package foo
+
+fun box(): String {
+    val chars = mapOf('\u0000' to 0x0000,
+                      '\u0001' to 0x0001,
+                      '\u0010' to 0x0010,
+                      '\u001F' to 0x001F,
+                      '\u0064' to 0x0064,
+                      '\u00A0' to 0x00A0,
+                      '\u00FF' to 0x00FF,
+                      '\u0100' to 0x0100,
+                      '\uF01F' to 0xF01F)
+
+    for ((char, code) in chars) {
+        assertEquals(code, char.toInt())
+        assertEquals(char, code.toChar())
+    }
+
+    return "OK"
+}