This patch adds a Linux implementation for signal
It also fixes ASSERT|EXPECT_THAT macros
OK with one naming fix suggested inline.
Neither POSIX nor std C prescribe it. Is it present merely as a convenience or because there is no way to describe function types using tablegen? Either way, I think this is OK. But to avoid name pollution, we should name this type with __ prefix.
Add a note that sigaction sets the errno value on error?