package/boost: boost needs wchar

package/boost: boost needs wchar

The most modules of boost needs a toolchain with wchar. To ease maintenance
we make the entire boost package depend on wchar.

Also add a reverse dependency to libftdipp1 and yaml-cpp.

Fixes:
http://autobuild.buildroot.net/results/49f/49f5c0521fc90fbd4673ad233ff679be007d2953/
http://autobuild.buildroot.net/results/12f/12f544c97e3451fb2a72025ebc62292957e47070/
http://autobuild.buildroot.net/results/ef6/ef6c897ea7547e8ed5f019e8ce4473f0998f2c16/
http://autobuild.buildroot.net/results/7a0/7a0ab069c505696a7887ba5c561b76b233ce59d5/

and more.

Signed-off-by: Jörg Krause <joerg.krause@embedded.rocks>
Acked-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>