libc/newlib: 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]
Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Message-Id: <d02252752d4dc5e68ae3.1349931202@localhost.localdomain>
PatchWork-Id: 190795

diff -durN gcc-3.4.6.orig/gcc/config/mips/t-linux gcc-3.4.6/gcc/config/mips/t-linux

--- gcc-3.4.6.orig/gcc/config/mips/t-linux	1970-01-01 01:00:00.000000000 +0100

+++ gcc-3.4.6/gcc/config/mips/t-linux	2007-08-15 23:08:15.000000000 +0200

@@ -0,0 +1,3 @@

+# Compile crtbegin/end with xgot so it works for both

+# normal and large GOTs.

+CRTSTUFF_T_CFLAGS = -mxgot