Respect version string in SubpluginArtifact to load compiler plugins

with versions different from compiler one

libraries/tools/kotlin-gradle-plugin-api/src/main/kotlin/org/jetbrains/kotlin/gradle/plugin/KotlinGradleSubplugin.kt

@@ -67,6 +67,6 @@ interface KotlinGradleSubplugin<in KotlinCompile : AbstractCompile> {
     fun getPluginArtifact(): SubpluginArtifact
 }
 
-open class SubpluginArtifact(val groupId: String, val artifactId: String)
+open class SubpluginArtifact(val groupId: String, val artifactId: String, val version: String? = null)
 
 class JetBrainsSubpluginArtifact(artifactId: String) : SubpluginArtifact(groupId = "org.jetbrains.kotlin", artifactId = artifactId)

libraries/tools/kotlin-gradle-plugin/src/main/kotlin/org/jetbrains/kotlin/gradle/plugin/KotlinPlugin.kt

@@ -695,7 +695,8 @@ internal class SubpluginEnvironment(
             project.logger.kotlinDebug { "Loading subplugin $pluginId" }
 
             val artifact = subplugin.getPluginArtifact()
-            val mavenCoordinate = "${artifact.groupId}:${artifact.artifactId}:$kotlinPluginVersion"
+            val artifactVersion = artifact.version ?: kotlinPluginVersion
+            val mavenCoordinate = "${artifact.groupId}:${artifact.artifactId}:$artifactVersion"
             project.logger.kotlinDebug { "Adding '$mavenCoordinate' to '$PLUGIN_CLASSPATH_CONFIGURATION_NAME' configuration" }
             project.dependencies.add(PLUGIN_CLASSPATH_CONFIGURATION_NAME, mavenCoordinate)