Adds Bidirectionality to Repeat
Fix Issue #8298, Don't throw exceptions on broken symlinks.

Using dirEntries to loop trough all the files/directories in a directory
will curently throw an Exception when encountering an broken symlink.

Whit this change DirEntry will no longer throw an Exception for broken
symlinks, but in that case isDir and isFile will return flase while
isSymlink returns true.
fix Issue 11780 - RangeError in format for incomplete format specifier
fix Issue 11403 - functions in std.algo can't be used as pred
Make std.container.Array assert.
Fix Take.back property
Take bidirectional unittest
Merge pull request #1631 from RommelVR/repeatbi

Adds Bidirectionality to Repeat
Remove dubious support for Unqual!R
Tweak blocks for consistency
Make internal attributes private
Tweak save implementation
tweak opDollar's DollarToken
new-style aliases
Use preconditions over asserts
rework slicing
Rework qualifiers in Cycle!Array
Use documented unittest in Repeat
Remove superfluous parens
More documented unittest