libunwind has a function to query whether the cursor points to a signal frame.
Use this to print
1: <signal handler called>
like GDB does, rather than printing something less useful such as
1: /usr/lib/libpthread.so.0 (funlockfile+0x60) [0x7f679838b870]
Signed-off-by: Aaron Plattner <aplattner@nvidia.com>
a73641937a