Compile with 64-bit kerberos on Windows

Hi, hackers.

I'm trying to build 64-bit windows binaries with kerberos support.
I downloaded latest kerberos source package from here:
https://kerberos.org/dist/index.html
I followed the the instructions in src\windows\README, and executed the
following script in 64-bit Visual Studio Command Prompt to build and
install it.

set NO_LEASH=1
set PATH=%PATH%;"%WindowsSdkVerBinPath%"\x86
set KRB_INSTALL_DIR=C:\krb5
cd src
nmake -f Makefile.in prep-windows
nmake NODEBUG=1
nmake install NODEBUG=1

To compile postgres with kerberos support, we need to configure the install
location in src/tools/msvc/config.pl
our $config = {gss => 'C:/krb5'};

If I run build.pl the compiler will complain about gssapi.h not found.
At src/tools/msvc/Solution.pm line 633, we can see the include directory is
set to '\inc\krb5'. This is no longer the case for 64-bit kerberos package.

The correct include directory is '\include'. The library paths also need to
be fixed with 64-bit version.

Here's a patch to fixed these paths, with this patch we can build 64-bit
binaries with kerberos support successfully.

Best regards,
Peifeng Qiu