Comment out TimeStamp structs for the moment

TSA part of the signature currently not implemented, but lets
leave the struct definitions here for later.
7 jobs for digital_signatures in 4 minutes and 26 seconds (queued for 5 seconds)
Status Job ID Name Coverage
  Build
passed #5073917
build

00:04:26

passed #5073922
build_android

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passed #5073918
build_clang_libcpp

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passed #5073921
build_clazy

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passed #5073920
build_mingw64_fedora

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passed #5073919
build_ubuntu_16_04

00:01:56

passed #5073916
clang_format

00:00:54