Problem building with F#4.0 - FsControl

[dtchepak]

Not sure if this issue belongs in Fleece or FsControl, but thought I'd let you know about it anyway. :)
gusty/FsControl#43

If I update the fsproj (dtchepak@8808caa) to build with F# 4 I get the following error when trying to build:

>c:\dev\git\fleece\Fleece\unknown(1,1): warning FS3186: An error occurred while reading the F# metadata node at positio
       n 878 in table 'ivals' of assembly 'FsControl.Core, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null'. The node h
       ad no matching declaration. Please report this warning. You may need to recompile the F# assembly you are using. [c:\d
       ev\git\fleece\Fleece\Fleece.fsproj]

[dtchepak]

Same problem build FsControl with F# 4.0