Always fix system DLL paths for 32bit programs

GetModuleFileNameEx might also return the 64bit system directory for 32bit
programs even for a 32bit gdb:

(gdb) info sharedlibrary
From        To          Syms Read   Shared Object Library
0x779d0000  0x77b34d20  Yes (*)     C:\Windows\SysWOW64\ntdll.dll
0x76850000  0x7694ad9c  Yes (*)     C:\Windows\syswow64\kernel32.dll
0x75421000  0x75466a18  Yes (*)     C:\Windows\syswow64\KernelBase.dll
0x6fbe1000  0x6fcca1c0  Yes (*)     C:\Windows\system32\dbghelp.dll
0x76d31000  0x76ddb2c4  Yes (*)     C:\Windows\syswow64\msvcrt.dll

So this makes the path conversion for all 32bit programs.

gdb/ChangeLog:

2020-03-27  Hannes Domani  <ssbssa@yahoo.de>

	* windows-nat.c (windows_add_all_dlls): Fix system dll paths.