Rename asm files so that they're picked up by cmake.
Split main cmake file into host and target parts.

This needs two trees to build the whole thing, buildit.sh script helps.
cross.toolchain tells cmake to not assume host system environment like
OSXROOT etc.
Changes to libc++ that were necessary to get it to compile for Metta.

Mostly disabling iostreams and wchar_t.
Some math.h and stdlib.h fiddling too.
This warning seems to be used only in more recent clang.

Revise after target toolchain upgrade.
Libc changes and additions to help with compiling libc++.
Merge branch 'libcxx-patches' into cmake-build