eval: Add luaeval function

No tests yet, no documentation update, no :lua* stuff, no vim module.

converter.c should also work with typval_T, not Object.

Known problem: luaeval("1", {}) results in

    PANIC: unprotected error in call to Lua API (attempt to index a nil value)

Ref #3823

scripts/generate_vim_module.lua

@@ -0,0 +1,38 @@
+assert(#arg == 2)
+
+module_file = arg[1]
+target_file = arg[2]
+
+module = io.open(module_file, 'r')
+target = io.open(target_file, 'w')
+
+target:write('#include <stdint.h>\n\n')
+target:write('static const uint8_t vim_module[] = {\n')
+
+num_bytes = 0
+MAX_NUM_BYTES = 15  -- 78 / 5: maximum number of bytes on one line
+target:write(' ')
+
+increase_num_bytes = function()
+  num_bytes = num_bytes + 1
+  if num_bytes == MAX_NUM_BYTES then
+    num_bytes = 0
+    target:write('\n ')
+  end
+end
+
+for line in module:lines() do
+  for i = 1,string.len(line) do
+    byte = string.byte(line, i)
+    assert(byte ~= 0)
+    target:write(string.format(' %3u,', byte))
+    increase_num_bytes()
+  end
+  target:write(string.format(' %3u,', string.byte('\n', 1)))
+  increase_num_bytes()
+end
+
+target:write('   0};\n')
+
+module:close()
+target:close()