[Design] command like function call

[khchen]

The Language Manual says:

Note that a call of form f(fn ... end) is a syntax sugar for f fn ... end where f is a function or a method that takes a single literal function as argument, like Lua.

This patch extends it: parentheses for closure/method calling can be omitted if first argument is fn, name, string, number, primitive, map, list, etc.

Example:

a = 123
sum = fn (a, b) return a + b end

print 1, 2, 3
print "a", "b", "c"
print sum 10, 20
print "x:", sum(10, 20), "y:", sum(30, 40)
print [1, 2, 3]
print {1: 1, 2: 2, 3: 3}
print fn return 123 end (),
  fn return 456 end ()

Output:

1 2 3
a b c
30
x: 30 y: 70
[1, 2, 3]
{2:2, 1:1, 3:3}
123 456