freerdp: Add support for uClibc

The stable-1.1 branch of freerdp fails to build when using a uClibc
toolchain because it's using functions which are not implemented in
uClibc, like eventfd_read, eventfd_write and futimes. That is causing
build failures like these ones:

../../libwinpr/synch/libwinpr-synch.so.0.1.0: undefined reference to
`eventfd_read'
../../libwinpr/synch/libwinpr-synch.so.0.1.0: undefined reference to
`eventfd_write'

../../common/libfreerdp-client.so.1.1.0: undefined reference to
`futimes'

Backport upstream patch, with non-applicable parts (new files from
master, but not in the stable-1.1 branch) trimmed down.

Upstream patch:
  https://github.com/FreeRDP/FreeRDP/commit/5f9c36da5d5cd3c5dce49f7b32fe011cb293f9ec/

Fixes:
  http://autobuild.buildroot.net/results/a66/a66e1ab18cd12904a64afcbf54116ceef889e966/build-end.log



Signed-off-by: Vicente Olivert Riera <Vincent.Riera@imgtec.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>