Recompile icu.net for icu 5.0 with proper version

The AssemblyVersion of icu.net.dll used by TeamCity builds is not the
same as for the icu.net.dll in the FieldWorks repository.  This is just
a recompilation with the fixed AssemblyVersion value.  (Having the same
AssemblyVersion seems to be important in practice, if not in theory.)

Change-Id: I50d169fbd1ff2ac6f6a78bf4b2c8837fd8049964