including lmpwindows.h globally from lmptype.h does more harm than good

this addresses some (cross) compilation issues locally.
in the long run, this should be addressed by implementing issue #1884
where platform specific functionality is wrapped into a small library
of generic functions adapted for LAMMPS' needs (like utils:: does for
non-portable convenience functions).

tools/lammps-shell/lammps-shell.cpp

@@ -22,6 +22,7 @@
 #if !defined(WIN32_LEAN_AND_MEAN)
 #define WIN32_LEAN_AND_MEAN
 #endif
+#include <direct.h>
 #include <io.h>
 #include <windows.h>
 #define chdir(x) _chdir(x)