Repeated import qualifiers accepted

[Paul D Anderson via Digitalmars-d]

Doubled (or tripled, etc.) import qualifiers are accepted in some 
cases.

auto m = std.math.std.math.std.math.abs(-32.33); // no error

std.stdio.std.stdio.writeln("123"); // no error

auto fmt = std.array.std.array.appender!(string)(); // no error

auto ms = std.mathspecial.std.mathspecial.gamma(0.5); // error 
"undefined identifier mathspecial"

import std.stdio.std.stdio : writeln; // error "module stdio is 
in file 'std/stdio/std' which cannot be read"

https://issues.dlang.org/show_bug.cgi?id=13192