patch 8.0.0693: no terminal emulator support

Problem:    No terminal emulator support.  Cannot properly run commands in the
            GUI.  Cannot run a job interactively with an ssh connection.
Solution:   Very early implementation of the :terminal command.  Includes
            libvterm converted to ANSI C.  Many parts still missing.
diff --git a/src/libvterm/vterm.pc.in b/src/libvterm/vterm.pc.in
new file mode 100644
index 0000000..c64c72d
--- /dev/null
+++ b/src/libvterm/vterm.pc.in
@@ -0,0 +1,9 @@
+prefix=@PREFIX@
+libdir=@LIBDIR@
+includedir=${prefix}/include
+
+Name: vterm
+Description: Abstract VT220/Xterm/ECMA-48 emulation library
+Version: @VERSION@
+Libs: -L${libdir} -lvterm
+Cflags: -I${includedir}