Bug fixes and compiler warnings. Unix readline support, pass 1

Fix various compiler warnings.

Fix bug causing double free when a file isn't found.

Fix bug using uninitialized variable parsing null filename.

Fix bug causing crash when format 3 retrieval pointer encountered.

Add support for readline (command line editing and history on Unix)

Untangle NT I/O so it builds without the direct access SCSI API & works.

Report errors as text messages everywhere.

Add MSVC project files.

Implement most of dir/full

Partially implement XABITM

Add help to command tables.

Allow choice of VMS qualifiers or Unix options.
  mount /write // /dev/cdrom
or
  mount -write /dev/cdrom

Parse quoted strings as command parameters.
   Mount /write "/dev/cdrom"
   search [*...]*.txt "My words for you"

Resolve command, parameter & qualifier ambiguity from tables.

Consolidate the various makefiles into a common file with very small
platform-specific wrappers.  This simplifies maintenance.

Add diskio module to allow easy access to .iso images and simulator files.
Removes requirement for loop device or equivalent.  Builds as a separate
executable.

Writes to the ODS2 volumes are broken.

extracters/ods2/compat.c

@@ -0,0 +1,78 @@
+/* Timothe Litt February 2016 */
+
+/* This module contains compatibility code, currently just
+ * to support Microsoft Windows.
+ *
+ * Microsoft deprecates sprintf, but doesn't supply standard
+ * replacement until very recent IDEs.
+ * Microsoft doesn't like fopen.
+ * One needs to use a M$ call to translate system errors.
+ */
+
+#if defined(_MSC_VER) && _MSC_VER < 1900
+
+#include <stdio.h>
+#include "compat.h"
+
+int c99_vsnprintf(char *outBuf, size_t size, const char *format, va_list ap)
+{
+    int count = -1;
+
+    if (size != 0)
+        count = _vsnprintf_s(outBuf, size, _TRUNCATE, format, ap);
+    if (count == -1)
+        count = _vscprintf(format, ap);
+
+    return count;
+}
+
+int c99_snprintf(char *outBuf, size_t size, const char *format, ...)
+{
+    int count;
+    va_list ap;
+
+    va_start(ap, format);
+    count = c99_vsnprintf(outBuf, size, format, ap);
+    va_end(ap);
+
+    return count;
+}
+
+#ifdef _WIN32
+#include <errno.h>
+#include <windows.h>
+
+FILE *openf( const char *filename, const char *mode ) {
+  errno_t err;
+  FILE *fd = NULL;
+
+  err = fopen_s( &fd, filename, mode );
+  if( err == 0 ) {
+    return fd;
+  }
+  return NULL;
+}
+
+
+TCHAR *w32_errstr( DWORD eno, ... ) {
+    va_list ap;
+    TCHAR *msg;
+
+    if( eno == 0 )
+        eno = GetLastError();
+    va_start(ap,eno);
+
+    if( FormatMessage( FORMAT_MESSAGE_ALLOCATE_BUFFER |
+        FORMAT_MESSAGE_FROM_SYSTEM, NULL, eno, 0,
+        (LPSTR)&msg, 1, &ap ) == 0 ) {
+        msg = (TCHAR *)malloc( 32 );
+        snprintf( msg, 32, "(%u)", eno );
+    }
+    va_end(ap);
+    return msg;
+}
+#endif
+#endif
+
+/* For ISO C compliance, ensure that there's something in this module */
+void dummy_compat ( void ) { return; }