Eliminate _assertPred
Fix DDoc typo.
Merge pull request #2031 from monarchdodra/ScopeBufferConst

Fix DDoc typo.
Merge pull request #2017 from andralex/datetime

std.datetime: eliminate _assertPred
OutBuffer is now an OutputRange
Merge pull request #2034 from WalterBright/OutBufferToOutputRange

OutBuffer is now an OutputRange