Fix MSVC scripts when building with GSSAPI/Kerberos

The deliverables of upstream Kerberos on Windows are installed with
paths that do not match our MSVC scripts.  First, the include folder was
named "inc/" in our scripts, but the upstream MSIs use "include/".
Second, the build would fail with 64-bit environments as the libraries
are named differently.

This commit adjusts the MSVC scripts to be compatible with the latest
installations of upstream, and I have checked that the compilation was
able to work with the 32-bit and 64-bit installations.

Special thanks to Kondo Yuta for the help in investigating the situation
in hamerkop, which had an incorrect configuration for the GSS
compilation.

Reported-by: Brian Ye
Discussion: https://postgr.es/m/162128202219.27274.12616756784952017465@wrigleys.postgresql.org
Backpatch-through: 9.6

src/tools/msvc/Solution.pm

@@ -1023,10 +1023,26 @@ sub AddProject
 	}
 	if ($self->{options}->{gss})
 	{
-		$proj->AddIncludeDir($self->{options}->{gss} . '\inc\krb5');
-		$proj->AddLibrary($self->{options}->{gss} . '\lib\i386\krb5_32.lib');
-		$proj->AddLibrary($self->{options}->{gss} . '\lib\i386\comerr32.lib');
-		$proj->AddLibrary($self->{options}->{gss} . '\lib\i386\gssapi32.lib');
+		$proj->AddIncludeDir($self->{options}->{gss} . '\include');
+		$proj->AddIncludeDir($self->{options}->{gss} . '\include\krb5');
+		if ($self->{platform} eq 'Win32')
+		{
+			$proj->AddLibrary(
+				$self->{options}->{gss} . '\lib\i386\krb5_32.lib');
+			$proj->AddLibrary(
+				$self->{options}->{gss} . '\lib\i386\comerr32.lib');
+			$proj->AddLibrary(
+				$self->{options}->{gss} . '\lib\i386\gssapi32.lib');
+		}
+		else
+		{
+			$proj->AddLibrary(
+				$self->{options}->{gss} . '\lib\amd64\krb5_64.lib');
+			$proj->AddLibrary(
+				$self->{options}->{gss} . '\lib\amd64\comerr64.lib');
+			$proj->AddLibrary(
+				$self->{options}->{gss} . '\lib\amd64\gssapi64.lib');
+		}
 	}
 	if ($self->{options}->{iconv})
 	{