avoid nullptr

Merge pull request rstudio#3737 from rstudio/bugfix/rstudio-v11-macos…

…-locale

port locale fix to v1.1

Merge pull request rstudio#3730 from rstudio/bugfix/regex-replace-c++…

…98-compatible

use functor instead of lambda

use 'query' variable

use 'query' variable

remove unused include

work around strange R 3.5.1 encoding issue

Open source companion commit for rstudio/rstudio-pro#479

remove C++11-isms

Fix some issues with running terminal on 64-bit rsession (Windows)

Fixes rstudio#2817

This has been somewhat non-deterministic. I'm seeing cases where
Win32 `executablePath()` returns an empty string, leading to mistakes
in locating the winpty.dll (and presumably other problems).
Also problems running terminal with 64-bit rsession build in dev
environment; hadn't tried that before, always used 32-bit.

Found some mention online that using `_pgmptr` for getting at
full path of current executable can have issues if used early in
startup, but it is safe to use `GetModuleFileName` early. So switched
to that approach.

Added an error log if there is a failure to find winpty.dll.

Made the decision on using 32-bit or 64-bit winpty.dll a compile-time
thing instead of runtime, since it's already known by virtue of which
rsession.exe is being built.