rename Void => Cvoid, Nothing (depending on usage)
git ls-files base doc src stdlib test | xargs perl -i -ple '/\b(ccall|cglobal|cfunction)\b/ && s/\bVoid\b/Cvoid/g'
git ls-files base doc src stdlib test | xargs perl -i -ple 's/\bPtr\{Void\}/Ptr{Cvoid}/g'
git ls-files base doc src stdlib test | xargs perl -i -ple 's/\Ref\{Void\}/Ref{Cvoid}/g'
perl -i -ple 's/\bVoid\b/Cvoid/g' base/atomics.jl base/libgit2/status.jl base/random/dSFMT.jl doc/src/manual/calling-c-and-fortran-code.md test/llvmcall.jl test/threads.jl
git ls-files base doc src stdlib test | xargs perl -i -ple 's/\bVoid\b/Nothing/g'
