Termcap update, replacing elvis by nvi.

Removing elvis, importing nvi, ctags, updating libedit.

Change-Id: I881eb04d2dc64cf112facd992de1114e1a59107f

usr.bin/nvi/docs/internals/context

@@ -0,0 +1,32 @@
+#	@(#)context	8.6 (Berkeley) 10/14/94
+
+In historic vi, the previous context mark was always set:
+
+ex address:
+    any number, <question-mark>, <slash>, <dollar-sign>,
+    <single-quote>, <backslash>
+
+ex commands: undo, "z.", global, v
+
+vi commands: (, ), {, }, %, [[, ]], ^]
+
+nvi adds the vi command ^T to this list.
+
+=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
+In historic vi, the previous context mark was set if the
+line changed:
+
+vi commands: '<mark>, G, H, L, M, z
+
+=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
+In historic vi, the previous context mark was set if the
+line or column changed:
+
+vi commands: `<mark>, /, ?, N, n
+
+nvi adds the vi command ^A to this list.
+
+=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
+In historic vi, the previous context mark was set in non-visual
+mode for ^R and ^L if the line changed, but I have yet to figure
+out how the line could change.