Update various WIN32-API functions to be wide-string aware.

Several NT API functions in Pike currently use the *A variants rather than the *W variants of functions. Eg _system.LookupAccountName() uses LookupAccountNameA() rather than LookupAccountNameW().

Non-exhaustive list of used NT functions:

• AcquireCredentialsHandleA
• CreateFileA
• ExpandEnvironmentStringsA
• GetNamedSecurityInfoA
• InetNtopA
• LogonUserA
• LookupAccountNameA
• LookupAccountSidA
• MoveFileExA
• QueryContextAttributesA
• QueryDosDeviceA
• QuerySecurityPackageInfoA
• RegEnumKeyExA
• RegEnumValueA
• RegOpenKeyExA
• RegQueryValueExA
• SetNamedSecurityInfoA

Update the code to be wide-string aware.

NB: Some of the above are currently accessed via aliases that look at UNICODE (and thus do not have an explicit A-suffix in the code).