Libdl does not recognise homedir

[AShedko]

When installing mxnet it did not install correctly, so i used a source distribution.
This line returns a ""
Libdl.find_library(["libmxnet", "libmxnet.so"], ["~/mxnet/lib"])
while
Libdl.find_library(["libmxnet", "libmxnet.so"], ["/home/ashedko/mxnet/lib"])
does return "/home/ashedko/mxnet/lib/libmxnet"

maybe consider permitting one to use ~ in paths in Libdl, as well as other

[yuyichao]

Dup of #1136. No function will do that automatically.