Support mmap on Windows
Don't export munmap
Small fixes discovered by testing on binary
Merge pull request #3603 from timholy/mmap

RFC: support mmap on Windows
Close #3390

I fixed this a while back but it was pending some other issue in Julia (most notably Int128 shifting). These have now been fixed/worked around.
don't copy parent string when serializing SubString. fixes #3646
fix hang in remotecall_fetch with error. fixes #3599
remove redundant timeit macro in testdefs
fix LOAD_PATH modification not to assume "." is in the array
add serialize and deserialize for BigInt and BigFloat
using strings for now, which is reliable and portable.
fixes #3643
fix #3651, codegen was missing some gc roots when boxing objects
Introduced ClusterManager. Externalized support for new cluster types.
moved addprocs_scyld and addprocs_sge to deprecated.jl