Fix inconsistent naming of fsiAnyCpu

On case-sensitive filesystems the
CopyDeployFilesToOutputDirectoryPreserveNewest step of the build of
fsiAnyCpu would fail because fsiAnyCpu.exe.config was named
fsiAnyCPU.exe.config:

/usr/lib/mono/4.0/Microsoft.Common.targets: error : Cannot copy
.../fsharp/src/fsharp/fsiAnyCpu/fsiAnyCpu.exe.config to
.../fsharp/lib/release/fsiAnyCpu.exe.config, as the source file
doesn't exist.

Renaming it and the fsproj makes camel-case use more consistent and
fixes the error.