keymap: add more (keypad) keycodes #9793

- K_KORIGIN instead of K_KCENTER: This name is similar to what is used
  by xev. Alternative could be K_KBEGIN as hinted here:
  https://invisible-island.net/xterm/ctlseqs/ctlseqs.html#h2-PC-Style-Function-Keys
  But I find Begin and Home too similar, and it might induced some
  confusion. The naming looked related to some old keyboard
  configuration.

- keymap.c: alias KPPeriod to kDel instead of kPoint.
  This might seems weird, but this is actually the behaviour that should
  be expected. libtermkey produces "KPPeriod" when num lock is off. To
  fix this would need to change this name in termkey.

closes #9780
closes #9793

src/nvim/keymap.c

@@ -163,6 +163,7 @@ static const struct key_name_entry {
   { K_DEL,             "Del" },
   { K_DEL,             "Delete" },      // Alternative name
   { K_KDEL,            "kDel" },
+  { K_KDEL,            "KPPeriod" },    // libtermkey name
   { K_UP,              "Up" },
   { K_DOWN,            "Down" },
   { K_LEFT,            "Left" },
@@ -171,6 +172,14 @@ static const struct key_name_entry {
   { K_XDOWN,           "xDown" },
   { K_XLEFT,           "xLeft" },
   { K_XRIGHT,          "xRight" },
+  { K_KUP,             "kUp" },
+  { K_KUP,             "KP8" },
+  { K_KDOWN,           "kDown" },
+  { K_KDOWN,           "KP2" },
+  { K_KLEFT,           "kLeft" },
+  { K_KLEFT,           "KP4" },
+  { K_KRIGHT,          "kRight" },
+  { K_KRIGHT,          "KP6" },
 
   { K_F1,              "F1" },
   { K_F2,              "F2" },
@@ -223,24 +232,36 @@ static const struct key_name_entry {
   { K_INS,             "Insert" },
   { K_INS,             "Ins" },         // Alternative name
   { K_KINS,            "kInsert" },
+  { K_KINS,            "KP0" },
   { K_HOME,            "Home" },
   { K_KHOME,           "kHome" },
+  { K_KHOME,           "KP7" },
   { K_XHOME,           "xHome" },
   { K_ZHOME,           "zHome" },
   { K_END,             "End" },
   { K_KEND,            "kEnd" },
+  { K_KEND,            "KP1" },
   { K_XEND,            "xEnd" },
   { K_ZEND,            "zEnd" },
   { K_PAGEUP,          "PageUp" },
   { K_PAGEDOWN,        "PageDown" },
   { K_KPAGEUP,         "kPageUp" },
+  { K_KPAGEUP,         "KP9" },
   { K_KPAGEDOWN,       "kPageDown" },
+  { K_KPAGEDOWN,       "KP3" },
+  { K_KORIGIN,         "kOrigin" },
+  { K_KORIGIN,         "KP5" },
 
   { K_KPLUS,           "kPlus" },
+  { K_KPLUS,           "KPPlus" },
   { K_KMINUS,          "kMinus" },
+  { K_KMINUS,          "KPMinus" },
   { K_KDIVIDE,         "kDivide" },
+  { K_KDIVIDE,         "KPDiv" },
   { K_KMULTIPLY,       "kMultiply" },
+  { K_KMULTIPLY,       "KPMult" },
   { K_KENTER,          "kEnter" },
+  { K_KENTER,          "KPEnter" },
   { K_KPOINT,          "kPoint" },
 
   { K_K0,              "k0" },