clang-tidy now also checks code in header files. Because the analyzer
finds tons of issues, activate the check only for directory "base/" (see
file ".clang-tidy"). All other directories, in particular "src/" are
left to future work.
While many findings were fixed, some were not (and suppressed instead).
Reasons for this include: a) the file is 1:1 copypaste of a 3rd-party
lib (e.g. pcg_extras.h) and fixing stuff would make upgrades/fixes more
difficult b) a fix would have broken lots of using code
This commit adds a number of changes to platform-detection and
compile-time directives required to support building ClickHouse on
Solaris-derived systems, most notably illumos.
