xformat -> format
Merge pull request #1286 from NilsBossung/xformat

remove the last traces of xformat
bigint purity
Merge branch 'master' into bigintpure

Conflicts:
	std/bigint.d
bigint pure

the only exception is toString as it takes a delegate and this makes
things more tricky
Merge pull request #1287 from burner/bigintpure

BigInt pure Fixed issus #6850