[commit: ghc] wip/erikd/rts's head updated: rts: Add `-Wundef` to CFLAGS and fix warnings (3c78114)

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Repository : ssh://git@git.haskell.org/ghc

Branch 'wip/erikd/rts' now includes:

     72b677d Fix Trac #12051
     ad7f122 Improve pretty-printing of equalities
     f9e90bc Improve documentation for type wildcards
     0bfcfd0 Comments only
     d1efe86 Comments only
     358567a testsuite: Add expected output for T11108
     470def9 Testsuite: fix T11827 (#11827)
     296b8f1 Add libraries/ghci/GNUmakefile to .gitignore [skip ci]
     f0f3517 Remove use of caddr_t
     8abc193 Get types in osFreeMBlocks in sync with osGetMBlocks
     464b6f8 {,M}BLOCK_SIZE_W * sizeof(W_) -> {,M}BLOCK_SIZE
     2e6433a testsuite: Add a TypeRep test
     a88bb1b Give lifted primitive types a representation
     1ee47c1 Use the correct return type for Windows' send()/recv() (Fix #12010)
     3c78114 rts: Add `-Wundef` to CFLAGS and fix warnings