Add support for Cygwin when handling temporary file names.  Improve error codes and diagnostic messages for temporary file name handling on Windows.  Rename winConvertUtf8Filename to winConvertFromUtf8Filename.  Improve placement and comments for forward function declarations.
Improve the consistency of the diagnostic messages on Windows.
Fix harmless MSVC compiler warning with MEMDEBUG defined.
Avoid commenting out #include statements when building the amalgamation source code file.
Reenable a test accidentally disabled when the stat4 branch was merged.
Enhancements to the Win32 API definition macros.
Fix a problem causing SQLite not to use stat4 or stat3 data to analyze constraints of the form "column = expr COLLATE collation" (those with an explicit COLLATE on the non-column side of the comparison operator).
Revise the amalgamation tool to allow 'duplicate' include files to be retained manually while still preserving the existing line numbers.
Cleanup of the windows VFS, including added support for Cygwin, fixes
for compiler warnings under unusual configurations, and improved diagnostic
error messages.