Option to use new URI for To header in processing call redirection

[nanang]

Currently call redirection will reuse the To header in the original redirected request as recommended by ​RFC3261 8.1.3.4. However, this may lead to this undesirable scenario:

1. B calls A, connected successfully (leg 1)
2. B calls C, C redirects to D, so B is connected to D (leg 2)
3. B transfers A to D (with replaces), but A ends up ringing C (instead of D)

It happens because in leg 2, B sees that it talks with C (reused original To header) and when transferring the call, B will use the remote URI (i.e: To header) for the Refer-To header in call transfer request. Using new URI for To header in processing call redirection will avoid such scenario.

Thanks Peter Koletzki for the report.

[nanang]

In 4347:

Close #1614: Added call redirect option PJSIP_REDIRECT_ACCEPT_REPLACE to accept call redirection with replaced 'To' header.