mpp_define_mosaic: Support Case where tile_id(1)>1

[J-Lentz]

Description
Currently, when a caller-defined tile_id list is passed to mpp_define_mosaic, it only works when the lowest tile ID in the list is 1. These changes add support for the case where the first tile ID is an integer greater than 1.

How Has This Been Tested?
Builds with ifx on C5, and fixes various array bounds errors in mpp_define_mosaic in my test case.

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• Any dependent changes have been merged and published in downstream modules
• New check tests, if applicable, are included
• make distcheck passes

[bensonr]

@J-Lentz - the comments at lines 1197-1198 address this issue. Either update the comments or use the suggested variable name.