edb-postgres.exe has encountered a problem on windows

Problem:
========

On windows when we run edb-postgres.exe without any command line args, its
getting crash or its showing error into Application logs of Event Viewer.

Analysis:
==========

For any stderr we call the write_stderr() and write_stderr() calls the
write_console() for stderr. Now here write_console() using the palloc()
internally, which require the CurrentMemoryContext.

At the startup CurrentMemoryContext will be NULL, so palloc again calling
write_stderr(). So recursion has been started and its ending up with
exception.

Call stack for palloc() is:

main() -> check_root() -> write_stderr() -> write_console() ->
pgwin32_toUTF16() -> palloc()

Fix:
=====

Earlier  we used to call vfprintf() for windows stderr, which is now
replaced with write_console().
So to avoid the exception now, I added condition for CurrentMemoryContext
into write_stderr().

PFA patch to fix the same.

Regards,
Rushabh Lathia
EnterpriseDB <http://www.enterprisedb.com/>, The Enterprise
PostgreSQL<http://www.enterprisedb.com/>
 company.