Highlight: Anonymous functions

[danielshahaf]

() { echo hello world } should consider echo a command word.

This is related to:

• () echo hello world (single-statement anonymous functions)
• f() { echo hello world } (normal function)
• f g h () { echo hello world } (with MULTI_FUNC_DEFS)
• { echo hello world } | … (inline blocks) (which are related to subshells: issue subshells highlighted as incorrect syntax #166)