@nogc for std.complex
annotate mathspecial functions
Merge pull request #2183 from jmdavis/datetime_ddoc_tests

Convert SysTime's examples to ddoc-ed unittests.
Merge pull request #2181 from WalterBright/annotate-math

annotate mathspecial functions
Merge pull request #2145 from WalterBright/nogc-complex

@nogc for std.complex
Make std.datetime.Date use ddoc-ed unittests.