Provide an Automatic-Module-Name for the netty-all artifact fixes #7644

Motivation:

The netty-all artifact doesn't have a Automatic-Module-Name defined in the manifest like the rest of the projects do, resulting in requires netty.all.

Modification:

Add Automatic-Module-Name

Result:

Correctly work as java9 module.

README.md

@@ -31,6 +31,7 @@ Netty can be used in modular JDK9 applications as a collection of automatic modu
 reverse-DNS style, and are derived from subproject names rather than root packages due to historical reasons. They
 are listed below:
 
+ * `io.netty.all`
  * `io.netty.buffer`
  * `io.netty.codec`
  * `io.netty.codec.dns`

all/pom.xml

@@ -664,6 +664,9 @@
                 <manifest>
                   <addDefaultImplementationEntries>true</addDefaultImplementationEntries>
                 </manifest>
+                <manifestEntries>
+                  <Automatic-Module-Name>io.netty.all</Automatic-Module-Name>
+                </manifestEntries>
                 <index>true</index>
               </archive>
             </configuration>