Change to use assert method.
Fix to not print unnecessary comma.

When `n2->car` is 0 and `n2->cdd` is not 0,
unnecessary comma was printed before first local variables.
Change to always use locals->car->car.

When p->locals->car is not NULL and p->locals->car->car is NULL,
local_add_f dose not append sym to p->locals->car->car.
This commit change to append sym to p->locals->car->car.
This will close #2333.
Add document for `add_conflict` and `add_conflicts`.
Add :doc task to run document generator.
Update document by regenerating it.
Fixed dead assignment in 'backtrace.c' reported by 'clang-analyzer'
Fixed dead assignment in 'parse.y' reported by 'clang-analyzer'
Fixed dead assignment in 'vm.c' reported by 'clang-analyzer'
Fixed possible division by zero in 'codegen.c' reported by 'clang-analyzer'
Fixed dead increment in 'dump.c' reported by 'clang-analyzer'
Fixed dereference to null pointer in 'codegen.c' reported by 'clang-analyzer'
Fixed dereference to null pointer in 'codegen.c' reported by 'clang-analyzer'
Revert "Fixed dereference to null pointer in 'codegen.c' reported by 'clang-analyzer'"

This reverts commit 29f14e728d319d9fc80702ba78959c1957944767.
Fixed dead assignment in 'parser.y' reported by 'clang-analyzer'
Fixed dead assignment in 'parser.y' reported by 'clang-analyzer'
Fixed dead assignment in 'parser.y' reported by 'clang-analyzer'
update add_confict document; ref #2391
git push origin masterMerge branch 'take-cheeze-conflict_doc'
Merge pull request #2392 from take-cheeze/doc_update

Update document and add :doc task.