windows: Update raw fetch/store operations

rawops.c is a hold over from Eric Williams' original attempt
to implement an AFS redirector.  When the rest of the his code
was purged from the tree and replaced with a more complete
implementation based upon the Kernel Drivers's File System
framework rawops.c was left behind.

Although the source file has been compiled as part of the build,
its functions ReadData and WriteData have never been called.  This
patchset:

 1. renames the functions to raw_ReadData and raw_WriteData

 2. modifies the function signatures and provides a header
    with prototypes

 3. requires that cm_scache.rw be write-locked upon entry

 4. renames variables

 5. removes the #define CM_BUF_BUFSIZE and relies upon
    cm_data.blockSize instead

 6. Always write back the current range as an async store
    instead of the previous chunk as random write patterns
    will fail to store all of the dirty buffers.

Change-Id: I1594b2950ab14da0c0de2a382fd1ba8248a9d1c6
Reviewed-on: http://gerrit.openafs.org/8953
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>
Tested-by: Jeffrey Altman <jaltman@your-file-system.com>