Rewrite code for capture rpfix

Rewrite code for capture rpfix

The previous code had many potential problems on the Windows side.
Targets of Windows native symbolic links (except those with
SYMBOLIC_LINK_RELATIVE set) and junction points are stored in the reparse
points as NT namespace paths.  Therefore they can validly include
prefixes like '\??\', '\DosDevices\', or '\Device\HardDiskVolume1'.  They
potentially do not use drive letters at all, and they may be over
MAX_PATH characters.  Such paths should be accessed using the native API
(NtOpenFile), not Win32 (CreateFile).  This commit changes the code to do
so.