Fixes #3259 -- Use placeholders when adding params to scope

Don't register nested variables of complex parameters as parameters of the compiled function. Use the computed placeholder name instead.
Handle backslashes at the end of heredocs
Add negative slice end index into docs
Merge pull request #3262 from xixixao/issue1766

Fix #1766, Add negative slice end index into docs
Implemented method call chaining
Handle nested calls and function oneliners when chaining
Added compilation regression test
Fixed leading whitespace before interpolation in simple strings
Fix #3264, missing leading whitespace before interpolation in heredoc
Merge pull request #3263 from xixixao/issue1495

Implement #1495,  Method call chaining
Merge pull request #3261 from xixixao/issue1273

Fix #1273, Handle backslashes at the end of heredocs
Improve HEREDOC regexp

  * Exclude trailing blank line from the match group
  * Fix backslash handling
через минус -> camelCase (респект Полу Миллеру)