freerdp: fix build with uClibc

freerdp: fix build with uClibc

Add upstream patch disabling use of C99 long double math functions (powl,
ceill, ...) that uClibc(-ng) don't have.

Fixes:
http://autobuild.buildroot.net/results/bda/bda53fffd4a0937fd4b2313cdf2d12ced95cc7a7/
http://autobuild.buildroot.net/results/d96/d9613c9f791157e1de3a34923f1c91b35cec693f/
http://autobuild.buildroot.net/results/bfd/bfd4ef86b257ee918e3c4463ebc5cf77694244a0/

Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>