libc/uClibc: Add CUSTOM version and CUSTOM_LOCATION config options and GetCustom

CUSTOM_LOCATION config options only presented in menuconfig if component
CUSTOM version selected.

Signed-off-by: "David Holsgrove" <david.holsgrove@xilinx.com>
[yann.morin.1998@free.fr: fix indentation, don't patch custom dir location]
Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Message-Id: <712995e3e719fbbe24af.1349931201@localhost.localdomain>
PatchWork-Id: 190794

 reporter_name="dsreed on freenode/#crosstool-ng"

 reporter_url=""

 reporter_comment="Enables experimental support for VFP/NEON hardware floating point."