Change format of -X arguments to require value after '='

Report a warning when an argument is passed in the old form (with the
whitespace)

 #KT-17264 Fixed

compiler/testData/cli/jvm/pluginSimpleUsage.args

@@ -1,7 +1,6 @@
 -d
 $TEMP_DIR$
--Xplugin
-dist/kotlinc/lib/android-extensions-compiler.jar
+-Xplugin=dist/kotlinc/lib/android-extensions-compiler.jar
 -P
 plugin\:org.jetbrains.kotlin.android\:package=com.myapp
 $TESTDATA_DIR$/pluginSimple.kt
@@ -11,4 +10,4 @@ $TESTDATA_DIR$/androidPlugin/androidWidget.kt
 $TESTDATA_DIR$/androidPlugin/fakeAppwidgetPackage.kt
 $TESTDATA_DIR$/androidPlugin/fakeInputMethodServicePackage.kt
 $TESTDATA_DIR$/androidPlugin/fakeOpenglPackage.kt
-$TESTDATA_DIR$/androidPlugin/fakeWebkitPackage.kt
+$TESTDATA_DIR$/androidPlugin/fakeWebkitPackage.kt