nfft: soname changes without package renaming and library transition

[Graham Inggs]

Package: libnfft3-double2
Version: 3.5.3-1
Severity: serious
Control: affects -1 src:pynfft python3-pynfft yorick-ynfft libnfft3-long2 libnfft3-single2

https://ci.debian.net/data/autopkgtest/testing/arm64/p/pynfft/24167703/log.gz

...
ERROR: Failure: ImportError (libnfft3_threads.so.2: cannot open shared object file: No such file or directory)
...

Files in first .deb but not in second
-------------------------------------
-rw-r--r-- root/root /usr/lib/x86_64-linux-gnu/libnfft3.so.2.0.0
-rw-r--r-- root/root /usr/lib/x86_64-linux-gnu/libnfft3_threads.so.2.0.0
lrwxrwxrwx root/root /usr/lib/x86_64-linux-gnu/libnfft3.so.2 -> libnfft3.so.2.0.0
lrwxrwxrwx root/root /usr/lib/x86_64-linux-gnu/libnfft3_threads.so.2 -> libnfft3_threads.so.2.0.0

Files in second .deb but not in first
-------------------------------------
-rw-r--r-- root/root /usr/lib/x86_64-linux-gnu/libnfft3.so.4.0.3
-rw-r--r-- root/root /usr/lib/x86_64-linux-gnu/libnfft3_threads.so.4.0.3
lrwxrwxrwx root/root /usr/lib/x86_64-linux-gnu/libnfft3.so.4 -> libnfft3.so.4.0.3
lrwxrwxrwx root/root /usr/lib/x86_64-linux-gnu/libnfft3_threads.so.4 -> libnfft3_threads.so.4.0.3

The same problem is present in libnfft3-long2 and libnfft3-single2.