std.mmfile: Improve error handling

Use wenforce instead of (inappropriately) errno.
Switch from if blocks to scope blocks.
std.mmfile: Fix Windows anonymous mapping creation to conform to MSDN
Merge pull request #2506 from CyberShadow/pull-20140909-232228

std.mmfile: Improve error handling
#6989 - attempt 1 on Tid.toString()
code formatting, use sink
update docs, style, use thread:id scheme