Upgrade to Kotlin 1.2

apiVersion and languageVersion options are set to 1.1
on production code in order to avoid incompatibilities
with Kotlin 1.1 based projects or libraries.

Issue: SPR-16239

Author: sdeleuze

build.gradle

@@ -14,7 +14,7 @@ buildscript {
 plugins {
 	id "com.gradle.build-scan" version "1.8"
 	id "io.spring.dependency-management" version "1.0.3.RELEASE" apply false
-	id "org.jetbrains.kotlin.jvm" version "1.1.61" apply false
+	id "org.jetbrains.kotlin.jvm" version "1.2.0" apply false
 	id "org.jetbrains.dokka" version "0.9.15"
 	id "org.asciidoctor.convert" version "1.5.6"
 }
@@ -50,7 +50,7 @@ configure(allprojects) { project ->
 	ext.junitJupiterVersion  = "5.0.2"
 	ext.junitPlatformVersion = "1.0.2"
 	ext.junitVintageVersion  = "4.12.2"
-	ext.kotlinVersion        = "1.1.61"
+	ext.kotlinVersion        = "1.2.0"
 	ext.log4jVersion         = "2.10.0"
 	ext.nettyVersion         = "4.1.17.Final"
 	ext.reactorVersion       = "Bismuth-SR4"
@@ -71,13 +71,19 @@ configure(allprojects) { project ->
 
 	apply plugin: "kotlin"
 	compileKotlin {
-		kotlinOptions.jvmTarget = "1.8"
-		kotlinOptions.freeCompilerArgs = ["-Xskip-runtime-version-check", "-Xjsr305=strict"]
+		kotlinOptions {
+			jvmTarget = "1.8"
+			freeCompilerArgs = ["-Xskip-runtime-version-check", "-Xjsr305=strict"]
+			apiVersion = "1.1"
+			languageVersion = "1.1"
+		}
 
 	}
 	compileTestKotlin {
-		kotlinOptions.jvmTarget = "1.8"
-		kotlinOptions.freeCompilerArgs = ["-Xskip-runtime-version-check", "-Xjsr305=strict"]
+		kotlinOptions {
+			jvmTarget = "1.8"
+			freeCompilerArgs = ["-Xskip-runtime-version-check", "-Xjsr305=strict"]
+		}
 	}
 
 	configurations.all {