Fix license headers (Followup #711)

Changeset was reviewed by @twall via preparation PR,
commit 093e349

Author: matthiasblaesing

checkstyle.xml

@@ -4,6 +4,9 @@
           "https://checkstyle.org/dtds/configuration_1_3.dtd">
 
 <module name="Checker">
+    <module name="SuppressionFilter">
+        <property name="file" value="checkstyle_suppressions.xml"/>
+    </module>
     <module name="FileTabCharacter"/>
     <module name="RegexpSingleline">
         <property name="format" value="\s+$"/>
@@ -16,4 +19,9 @@
     <module name="TreeWalker">
         <module name="Indentation"/>
     </module>
+    <module name="RegexpHeader">
+        <property name="id" value="header-check" />
+        <property name="headerFile" value="checkstyle_header.txt"/>
+        <property name="multiLines" value="2"/>
+    </module>
 </module>

checkstyle_header.txt

@@ -0,0 +1,23 @@
+^/\*( Copyright.*$|$)
+^ \*( Copyright.*$|$)
+^ \* The contents of this file is dual-licensed under 2$
+^ \* alternative Open Source/Free licenses: LGPL 2\.1 or later and$
+^ \* Apache License 2\.0\.( \(starting with JNA version 4\.0\.0\)\.$|$)
+^ \*$
+^ \* You can freely decide which license you want to apply to$
+^ \* the project\.$
+^ \*$
+^ \* You may obtain a copy of the LGPL License at:$
+^ \*$
+^ \* http://www\.gnu\.org/licenses/licenses\.html$
+^ \*$
+^ \* A copy is also included in the downloadable source code package$
+^ \* containing JNA, in file "LGPL2\.1"\.$
+^ \*$
+^ \* You may obtain a copy of the Apache License at:$
+^ \*$
+^ \* http://www\.apache\.org/licenses/$
+^ \*$
+^ \* A copy is also included in the downloadable source code package$
+^ \* containing JNA, in file "AL2\.0"\.$
+^ \*/$