issue 5224
fix Issue 10125 Unicode non-BMP decoding to dchar in stdio readln

strings were first decoded to wchars, each wchar was then separately
decoded to dchar, resulting in 2 dchars in the surrogate block instead
of 1 correct dchar.

added unit test to verify readln decoding of non-ASCII characters
Merge branch 'master' of github.com:D-Programming-Language/phobos into 5224
@blackwhale's review
@blackwhale's destruction
combine some statements
Fix issue 10601.

If extension is empty, std.path.setExtension should be equivalent to
std.path.stripExtension. This special case is useful in generic code
that needs to alternate between, e.g., .exe on Windows and no executable
extension on Posix.
Simplify unittest.
Fix issue# 10717.

This makes it so that if you're operating on chars or wchars with
std.ascii functions, you don't have to cast the return values back to
char or wchar, but it still allows you to operate on dchars without
mangling any Unicode values.
Merge pull request #1409 from quickfur/issue10601

Fix issue 10601.
Merge pull request #1162 from andralex/5224

Fix Issue 5224 - std.algorithm.remove!(SwapStrategy.unstable) doesn't work
fix Issue 10732 - Example code for std.utf.toUTFindex does not work
[trivial] fix code style
[trivial] Use ddoc unittest
[trivial] unittest code clean up
Make std.utf module CTFEable
Merge pull request #1443 from 9rnsr/CTFEablePhobos

Make std.utf module CTFEable
Add document for memory safety of std.conv.toImpl for char* to string conversion
Merge pull request #1446 from tom-tan/add-conv-toImpl-comment

Add document for memory safety of toImpl for char* to string conversion.

Merged.
Merge pull request #1436 from jmdavis/10717

Fix issue# 10717.

Merged.