Allow optional arguments on macro tags

[marcioAlmada]

Macro tags are flags that serve as meta information #4. Turns out it may be a good thing to allow macro tags to have arguments:

macro ·name('MyMacro') { /* match */ } >> { /* expansion */ }

Blocks #15

[marcioAlmada]

For example, a ·name() tag could be useful to give better error messages for dominant macros #6.

Before:
Unexpected ';' on line 1, expected '{'

After:
Unexpected ';' on line 1, expected '{' while expanding "unless" macro