unqual

update unittests
std.complex: clean imports
std.conv: clean imports
Use scope imports in std.net.isemail

remove commented code
base64: update to range.constraints
Merge pull request #2722 from 9il/im

Use scope imports in std.net.isemail
Merge pull request #2707 from 9il/rc-base64

base64: update to range.constraints
Merge pull request #2706 from 9il/complex

std.complex: clean imports
Merge pull request #2705 from 9il/conv2

std.conv: clean imports
Merge pull request #2638 from 9il/unqual

Allow std.numeric works with const ranges