Deprecate g_tls_client_connection_copy_session_state()

Exposing this function in the GLib API was probably a mistake. It has no
users anywhere in Debian, and it's currently impossible to ensure it
actually does anything.
12 jobs for mcatanzaro/copy-session-state in 76 minutes and 58 seconds (queued for 3 seconds)
latest
Status Job ID Name Coverage
  Build
passed #391909
cross-android_api21_arm64

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passed #391910
cross-android_api28_arm64

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passed #391911
cross-mingw64

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passed #391907
debian-stable-x86_64

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passed #391906
fedora-x86_64

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passed #391914
freebsd-11
freebsd-11-x86_64

00:06:22

passed #391915
freebsd-12
freebsd-12-x86_64

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passed #391908
G_DISABLE_ASSERT

00:02:20

passed #391912
win32
msys2-mingw32

00:54:43

passed #391913
win32
vs2017-x64

00:09:26

 
  Coverage
passed #391916
coverage

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77.9%
 
  Analysis
passed #391917
scan-build

00:04:38