BUG #3909: src\tools\msvc\clean.bat clears parse.h file

The following bug has been logged online:

Bug reference:      3909
Logged by:          Pavel Golub
Email address:      pavel@gf.microolap.com
PostgreSQL version: 8.3RC2
Operating system:   WinXP
Description:        src\tools\msvc\clean.bat clears parse.h file
Details: 

Executing clean.bat from src\tools\msvc clears src\backend\parser\parse.h

However, in help stated:

"Bison and Flex are required to build from CVS, but not required when
building from a release file."

Also in src\backend\parser\Makefile we have comments:

"# gram.c, parse.h, and scan.c are in the distribution tarball, so they
# are not cleaned here."

Because of this bug there is no opportunity to build PostgreSQL by Visual
Studio without using Bison.

So, may be as a workaround we may use such scheme:
1. We have "src\backend\parser\parse.h.release" (or whatever postfix) file
2. GenerateFiles() in Solution.pm must check if Bison is available. If so
then generate parse.h by Bison, else copy parse.h.release as parse.h
3. When clean will be called parse.h will be deleted, but not
parse.h.release

Regards