+/*
+ * PS/2 Scan Code Set 2: Exceptional Handling
+ *
+ * There are several keys to be handled exceptionally.
+ * The scan code for these keys are varied or prefix/postfix'd
+ * depending on modifier key state.
+ *
+ * References:
+ * http://www.microsoft.com/whdc/archive/scancode.mspx
+ * http://download.microsoft.com/download/1/6/1/161ba512-40e2-4cc9-843a-923143f3456c/scancode.doc
+ *
+ *
+ * Insert, Delete, Home, End, PageUp, PageDown, Up, Down, Right, Left:
+ * Num Lock: off
+ * modifiers | make | break
+ * ----------+---------------------------+----------------------
+ * Ohter | <make> | <break>
+ * LShift | E0 F0 12 <make> | <break> E0 12
+ * RShift | E0 F0 59 <make> | <break> E0 59
+ * L+RShift | E0 F0 12 E0 F0 59 <make> | <break> E0 59 E0 12
+ *
+ * Num Lock: on
+ * modifiers | make | break
+ * ----------+---------------------------+----------------------
+ * Other | E0 12 <make> | <break> E0 F0 12
+ * Shift'd | <make> | <break>
+ *
+ * Handling: ignore these prefix/postfix codes
+ *
+ *
+ * Keypad-/:
+ * modifiers | make | break
+ * ----------+---------------------------+----------------------
+ * Ohter | <make> | <break>
+ * LShift | E0 F0 12 <make> | <break> E0 12
+ * RShift | E0 F0 59 <make> | <break> E0 59
+ * L+RShift | E0 F0 12 E0 F0 59 <make> | <break> E0 59 E0 12
+ *
+ * Handling: ignore these prefix/postfix codes
+ *
+ *
+ * PrintScreen:
+ * With hoding down modifiers, the scan code is sent as following:
+ *
+ * modifiers | make | break
+ * ----------+--------------+-----------------------------------
+ * Other | E0 12 E0 7C | E0 F0 7C E0 F0 12
+ * Shift'd | E0 7C | E0 F0 7C
+ * Control'd | E0 7C | E0 F0 7C
+ * Alt'd | 84 | F0 84
+ *
+ * Handling: ignore prefix/postfix codes and treat both scan code
+ * E0 7C and 84 as PrintScreen.
+ *
+ * Pause:
+ * With hoding down modifiers, the scan code is sent as following:
+ *
+ * modifiers | make(no break code)
+ * ----------+--------------------------------------------------
+ * no mods | E1 14 77 E1 F0 14 F0 77
+ * Control'd | E0 7E E0 F0 7E
+ *
+ * Handling: treat these two code sequence as Pause
+ *
+ */