[CMake] [ANNOUNCE] CMake 3.15.6 available for download

[Robert Maynard]

We are pleased to announce that CMake 3.15.6 is now available for download.

Please use the latest release from our download page:
  https://cmake.org/download/

Thanks for your support!

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Changes in 3.15.6 since 3.15.5:

Alexander Grund (1):
  Check for support before adding bigtoc linker flag

Ben Boeckel (1):
  FindPostgreSQL: support version encoding used in pre-10 releases

Brad King (4):
  CMakeParseImplicitIncludeInfo: Remove all CR chars from compiler output
  VS: Fix support for v142 toolset minor versions in VS 16.5+
  FindBLAS: Consider OpenBLAS with thread libraries only with C or CXX
  CMake 3.15.6

Deniz Bahadir (1):
  FindBoost: Prevent warning due to new meta-component "ALL" of Boost 1.73

Markus Mittendrein (1):
  FindGTK2: Add harfbuzz to GTK2_INCLUDE_DIRS