test/ros3.c and test/s3comms.c each had a 'FUNC' that needed to be
'__func__', missed in a previous merge.
* Cleans up POSIX/C bits in H5private.h
* Assume difftime exists (C89)
* Reorg AC_CHECK_HEADERS so headers are in alphabetical order
* Split off networking-related AC_CHECK_HEADERS
* Remove unused UNAME_CYGWIN from configure.ac
* Remove checks for unused sys/timeb.h
* Tidying pass over H5private.h HD prefix macros
* Tidy H5win32defs.h
* Add HD prefix to various scanf calls
* Committing clang-format changes
* Fixes to the alarm(2) code used in the tests to make Windows happy
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