follow and test macros 2.0

[Geal]

a new macro system is coming and should replace the previous macro system (macro_rules) at some point.
How to plan the migration to the new system? I'll probably make a reduced version of nom to test stuff, and get a feel of the syntax.
It might be good to have two versions of the code during the transition period (maybe hidden behind a module and feature or something)

[Geal]

issues to follow:

• macros 2.0 RFC
• Tracking issue: declarative macros 2.0
• roadmap
• syntax for multiple matches
• Tracking issue for "macro naming and modularisation" (RFC #1561)
• Initial implementation of declarative macros 2.0

[Geal]

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