Update version and jnr-ffi for release

Author: headius

pom.xml

@@ -4,7 +4,7 @@
   <groupId>com.github.jnr</groupId>
   <artifactId>jnr-posix</artifactId>
   <packaging>jar</packaging>
-  <version>3.1.21-SNAPSHOT</version>
+  <version>3.1.21</version>
   <name>jnr-posix</name>
   <description>
     Common cross-project/cross-platform POSIX APIs
@@ -73,7 +73,7 @@
     <dependency>
       <groupId>com.github.jnr</groupId>
       <artifactId>jnr-ffi</artifactId>
-      <version>2.2.17</version>
+      <version>2.2.18</version>
     </dependency>
     <dependency>
       <groupId>com.github.jnr</groupId>