Bug and memory leaks with access to file links with long names (Windows, MSVS)

Hi!

PostgreSQL build under Windows with MS Visual Studio has functions to
work with
links (unlike msys2 that has own functions). If a database has link
pointing
to location longer 130 chars, function pgreadlink fails to recognise
this
link and cancels query.
The reason of the error - small buffer for link name - MAX_PATH
symbols, though this
buffer must have the place for at least 2 MAX_PATH : substitution and
print names
of the link.

How to reproduce:

If build directory has length ~100 chars or longer,
pg_rewind/004_pg_xlog_symlink
test will fail (Windows, MSVS build)

Steps to reproduce:

call "C:\Program Files\Microsoft Visual
Studio\2022\Community\VC\Auxiliary\Build\vcvarsall.bat" x64
SET LC_MESSAGES=C

SET
BUILDDIR=c:\postgresql-builds\length_30\length_40\length_50\length_60\length_70\length_80\length_90\length100\
meson setup %BUILDDIR% --prefix=c:\postgresql-builds\install
c:
cd %BUILDDIR%
meson compile -C %BUILDDIR%
meson install -C %BUILDDIR%
meson test -C %BUILDDIR%

Memory leak:
In case of error the function in the code branch reporting the error
does not return
Windows file handle and Windows heap allocation for error message text.

Solution:
Proposed patch fixes link information buffer size changing it to the
documented value
MAXIMUM_REPARSE_DATA_BUFFER_SIZE,
and fixes memory leaks - the message buffer copied to a buffer on stack
with maximal message size 64Kb.

--
Best regards,

Vladlen Popolitov.