[Flang][OpenMP] Avoid abort when collapse clause value is negative

[Flang][OpenMP] Avoid abort when collapse clause value is negative

Summary:
If the value in the collapse close is negative f18 abort without the correct error message. This PR change the size_t in name resolution to a int64_t and check appropriately for negative or zero before the privatization of induction variable.
The correct error is then catch by the OpenMP structure check.

This diff is migrated from the GitHub pull request https://github.com/flang-compiler/f18/pull/1098

Reviewers: ichoyjx, jdoerfert, sscalpone, DavidTruby

Reviewed By: ichoyjx, sscalpone, DavidTruby

Subscribers: sscalpone, klausler, yaxunl, guansong, llvm-commits

Tags: #llvm, #flang

Differential Revision: https://reviews.llvm.org/D77821