[PATCH] Rename header guards to be consistent with upstream project's conventions.

[Thomas Rodgers]

Tested x86_64-linux, committed to trunk.

Jonathan Wakely writes:

> On 29/05/19 15:30 -0700, Thomas Rodgers wrote:
>>
>>	* include/pstl/glue_memory_impl.h: Rename all macros of the form
>>	_PSTL_(.*)_H to _PSTL_\U\1_H.
>>	* include/pstl/numeric_impl.h: Likewise.
>>	* include/pstl/glue_memory_defs.h: Likewise.
>>	* include/pstl/execution_defs.h: Likewise.
>>	* include/pstl/utils.h: Likewise.
>>	* include/pstl/algorithm_fwd.h: Likewise.
>>	* include/pstl/unseq_backend_simd.h: Likewise.
>>	* include/pstl/glue_execution_defs.h: Likewise.
>>	* include/pstl/algorithm_impl.h: Likewise.
>>	* include/pstl/parallel_impl.h: Likewise.
>>	* include/pstl/memory_impl.h: Likewise.
>>	* include/pstl/glue_numeric_defs.h: Likewise.
>>	* include/pstl/parallel_backend_utils.h: Likewise.
>>	* include/pstl/glue_algorithm_defs.h: Likewise.
>>	* include/pstl/parallel_backend.h: Likewise.
>>	* include/pstl/glue_numeric_impl.h: Likewise.
>>	* include/pstl/parallel_backend_tbb.h: Likewise.
>>	* include/pstl/numeric_fwd.h: Likewise.
>>	* include/pstl/glue_algorithm_impl.h: Likewise.
>>	* include/pstl/execution_impl.h: Likewise.
>>	* include/pstl/pstl_config.h: Likewise.
>>	* testsuite/util/pstl/pstl_test_config.h: Likewise.
>
> OK for trunk, thanks.