__ZRT_HOST TLS enabled; added configure into .gitignore

x86_64 TLS enabled, thus nacl-tls code disabled;
errno, h_errno TLS variables converted to generic
for __ZRT_HOST 64bit datatypes are supported
preinit zcall added; mainly for __ZRT_HOST
__ZRT_HOST support: pagesize=4K is hardcoded, it's the same as used on ubuntu linux
configure option --with-zrt extended with value 'forhost'

__ZRT_HOST support added into configure, --with-zrt=forhost must be
used when building for host;
Merge pull request #20 from YaroslavLitvinov/dev

zrt host support