use Pratt's parser for expressions in the {log} block

[PK1A]

This PR contains 2 commits:

• 5c10af9 - support for multi-statement expressions
• 8fe2be8 - the actual switch of expression parsing for the {log} block

Please note that the second commit is actually removing more code than it is adding :-)

[benouat]

LGTM. Could be merged 👍 (apart my really small comment above)

[PK1A]

Landed as 96c91ad. Thnx for the suggestion @benouat - I'm going to open a separate PR to move to the https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/isArray polyfill for the bullet-proof detection of arrays.