Fix MSVC compatibility issues

Project now builds in Visual Studio 2017, probably earlier versions
too as long as they support enough of C99.

hooklib/meson.build

@@ -1,7 +1,10 @@
 hooklib_lib = static_library(
     'hooklib',
     include_directories : inc,
-    c_pch : '../precompiled.h',
+    c_pch : [
+        '../precompiled.c',
+        '../precompiled.h',
+    ],
     sources : [
         'serial.c',
         'serial.h',

hooklib/serial.c

@@ -1,6 +1,10 @@
 #include <windows.h>
 
+#ifdef __GNUC__
 #include <ntdef.h>
+#else
+#include <winnt.h>
+#endif
 #include <devioctl.h>
 #include <ntddser.h>
 

hooklib/uart.c

@@ -1,6 +1,10 @@
 #include <windows.h>
 
+#ifdef __GNUC__
 #include <ntdef.h>
+#else
+#include <winnt.h>
+#endif
 #include <devioctl.h>
 #include <ntddser.h>
 

hooklib/uart.h

@@ -2,7 +2,11 @@
 
 #include <windows.h>
 
+#ifdef __GNUC__
 #include <ntdef.h>
+#else
+#include <winnt.h>
+#endif
 #include <devioctl.h>
 #include <ntddser.h>