Supports xl8 of spots in epilogue of rip-rel mangling, e.g. caused by an asynch signal. This patch adds support to advance the program counter properly as described in xref #3307 for the simplest case, which is rip-rel mangled instruction not part of another mangled region. These simple mangling epilogue instructions are marked with a new flag, and checks have been added to constrain this to the simplest case.
Adds XXX i#3307 comments to parts in mangling that need to get reviewed.
Adds 2 tests. The test client.mangle_suspend reliably exposes bug as described above.
Issue: #3307 Fixes #2941 (closed)