[Chapel Merge] update spec to clarify that serial,local blocks al

Branch: refs/heads/master
Revision: e8ad21e
Author: mppf
Log Message:

Merge pull request #17343 from mppf/spec-local-serial-split-elide

update spec to clarify that serial,local blocks allowed for split-init, copy-elision

Follow-up to PRs #17258 and #17285.

Document in spec that serial and local blocks are allowed for split init
and copy elision.

Note that the local block is documented in the technote:

The ‘local’ keyword — Chapel Documentation 1.23

but the serial block is in the spec

Task Parallelism and Synchronization — Chapel Documentation 1.23

Reviewed by @bradcray - thanks!

Modified Files:
M doc/rst/language/spec/variables.rst

Compare: https://github.com/chapel-lang/chapel/compare/75b7e7df26c5...e8ad21e4d74d