Improve comment spelling and style in llvmjit_deform.c.
Improve comment spelling and style in llvmjit_deform.c.

Author: Justin Pryzby
Discussion:
    https://postgr.es/m/20190408141828.GE10080@telsasoft.com
    https://postgr.es/m/20181127184133.GM10913@telsasoft.com

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