#81 Fix VS2019 Code Analysis warnings

[Pete Batard]

When compiling for x64, Visual Studio 2019's Code Analysis produces the following warnings:

C:\Projects\gnu-efi\lib\print.c(1380): warning C26451: Arithmetic overflow: Using operator '+' on a 4 byte value and then casting the result to a 8 byte value. Cast the value to the wider type before calling operator '+' to avoid overflow (io.2).
C:\Projects\gnu-efi\lib\smbios.c(47): warning C26451: Arithmetic overflow: Using operator '+' on a 4 byte value and then casting the result to a 8 byte value. Cast the value to the wider type before calling operator '+' to avoid overflow (io.2).
C:\Projects\gnu-efi\lib\str.c(289): warning C26451: Arithmetic overflow: Using operator '-' on a 4 byte value and then casting the result to a 8 byte value. Cast the value to the wider type before calling operator '-' to avoid overflow (io.2).

Fix these by adding an explicit cast to UINTN.

[Nigel Croxon]

commit 4ef183353cd98e8d0e9ef0c5bbe7783ff10da891 (HEAD -> master)
Author: Pete Batard pete@akeo.ie
Date: Thu Jul 15 12:38:22 2021 +0100

Fix VS2019 Code Analysis warnings