KT-5214 Annotation to provide platform name to avoid signature conflict

#KT-5214 Fixed

compiler/testData/compileKotlinAgainstKotlin/PlatformNames.A.kt

@@ -0,0 +1,12 @@
+package lib
+
+import kotlin.platform.*
+
+[platformName("bar")]
+fun foo() = "foo"
+
+var v: Int = 1
+    [platformName("vget")]
+    get
+    [platformName("vset")]
+    set

compiler/testData/compileKotlinAgainstKotlin/PlatformNames.B.kt

@@ -0,0 +1,8 @@
+import lib.*
+
+fun main(args: Array<String>) {
+    foo()
+
+    v = 1
+    println(v)
+}