Add a function `deleteSubmap`#2

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QuietJoon wants to merge 5 commits intomichaeljklein:masterfrom

QuietJoon:deleteSubmap

Commits on May 12, 2020

Commits on May 16, 2020

Add missing function export
QuietJoon
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Commits on Oct 1, 2020

Relax upper bound for GHC 8.8.*
QuietJoon
committed