doc: include linux/input.h verbatim in the documentation

This makes it easier to look up what specific version libevdev was compiled
against.

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
Reviewed-by: Benjamin Tissoires <benjamin.tissoires@gmail.com>

doc/libevdev.doxygen.in

@@ -713,7 +713,7 @@ EXCLUDE_SYMBOLS        =
 # directories that contain example code fragments that are included (see
 # the \include command).
 
-EXAMPLE_PATH           =
+EXAMPLE_PATH           = @top_srcdir@/include
 
 # If the value of the EXAMPLE_PATH tag contains directories, you can use the
 # EXAMPLE_PATTERNS tag to specify one or more wildcard pattern (like *.cpp

libevdev/libevdev.h

@@ -470,6 +470,15 @@ extern "C" {
  *
  */
 
+/**
+ * @page kernel_header Kernel header
+ *
+ * libevdev provides its own copy of the Linux kernel header file and
+ * compiles against the definitions define here. Event type and event code
+ * names, etc. are taken from the file below:
+ * @include linux/input.h
+ */
+
 /**
  * @defgroup init Initialization and setup
  *