Compilation error with Java 21

[cushon]

The definition of SIPHeaderList#removeLast causes a compilation error with Java 21:

jsip/src/gov/nist/javax/sip/header/SIPHeaderList.java

Line 289 in bbf3067

public void removeLast() {

The change is due to the introduction of 'Sequenced Collections' in JDK 21 release notes, which added a removeLast method to the collections API that clashes with the definition in SIPHeaderList.

The error could be fixed by changing the definition of SIPHeaderList#removeLast to match the definition in the collections API, or by renaming the method.

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Repro:

JAVA_HOME=<path to JDK 21> ant -Djavac.source=8 -Djavac.target=8 -Dsource.encoding=iso-8859-1 runtck

[jain-javac] /usr/local/google/home/cushon/src/jsip/src/gov/nist/javax/sip/header/ims/ServiceRouteList.java:37: error: removeLast() in SIPHeaderList cannot implement removeLast() in List
[jain-javac] public class ServiceRouteList extends SIPHeaderList<ServiceRoute> {
[jain-javac]        ^
[jain-javac]   return type void is not compatible with ServiceRoute
[jain-javac]   where E is a type-variable:
[jain-javac]     E extends Object declared in interface List