Fix a couple of ordinary and pedantic warnings

Add previously missing -Wall to warning flags in CMake. Remove -Wformat
and -Wvariadic-macros (enabled by default; latter is not meaningful in
C99 mode we use), -Wdeclaration-after-statement (again, not needed as
we use C99). Move -Wmissing-declarations to C-only flags (GCC man says
so).

Add copyrights year to crypto-utils-fallback.c.


git-svn-id: svn://svn.transmissionbt.com/Transmission/trunk@14370 f4695dd4-2c0a-0410-b89c-da849a56a58e