Improve support for UNC paths

[fekir]

mc seems to only partially support UNC paths, which are sometimes required for accessing specific files and folders.

# does not start mc in the C:\ folder
mc "\\?\C:\"

# start mc in the C:\Users folder
mc "\\?\C:\Users"

in the second case, the content of the directory is not shown correctly

Typing cd \\?\C:\Users command in mc causes an error, while cd C:\Users works

[adamyg]

Attempt to utilize forward not backlashes, currently limited to network drives "\\server\share\path\file"

https://learn.microsoft.com/en-us/windows/win32/fileio/naming-a-file?redirectedfrom=MSDN

`the "\?" prefix to a path string tells the Windows APIs to disable all string parsing and to send the string that follows it straight to the file system. For example, if the file system supports large paths and file names, you can exceed the MAX_PATH limits that are otherwise enforced by the Windows APIs.

Because it turns off automatic expansion of the path string, the "\?" prefix also allows the use of ".." and "." in the path names, which can be useful if you are attempting to perform operations on a file with these otherwise reserved relative path specifiers as part of the fully qualified path.
`

Not a conventional path. The internals of mc wont support file names using the "." and ".." within paths, these shall always be treated and current and sub-directory.

Shall review the path parser, only option ignore leading "//?" and "\\?", treat remaining as a normal path.

[fekir]

Shall review the path parser, only option ignore leading "//?" and "\?", treat remaining as a normal path.

While it fixes the issue presented here, a better solution would be to fully support it.

Currently mc seem unable to access in any was a folder named, for example, test. (leading dot), which is accessible from the shell (powershell) when using UNC.
Other programs (cygwin shell, far file manager, ...) do not even need to use UNC paths for accessing it (as they do the conversion internally, providing a more consistent experience to the end-user)

[fekir]

For completeness, in case of a folder ending with . the content is not shown correctly

The folder ab. is shown colored as ?ab., and the permission are missing.
The folder test, which is in the same directory, is shown correctly.

Pressing enter on ab. shows following dialog

[adamyg]

Appreciate the feedback, shall see what is practical within confines of the mc-core engine.