This patch improves the LIT tests on the following :
- The test on uses_allocators clause in the target region by adding the respective CHECK lines. Allocator omp_thread_mem_alloc is also added in the test.
- The defaultmap clause wasn't being tested for the variable-category scalar and the implicit-behavior tofrom with respect to the OpenMP default version.
These improvements are inspired from SOLLVE tests.
SOLLVE repo: https://github.com/SOLLVE/sollve_vv
This should go into the _messages test case