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Merge trunk. Another round of (harmless) -Wconversion fixes

Merge 9.0

Rebase to trunk

Missing Tcl_DStringFree()

Another bunch of -Wconversion warning fixes

amend (unsaved changes, missing (tracePtr = cmdPtr->tracePtr) by clea…

…n-up)

Proposed fix for [17960b80db]: Missing libtcl?.?.dll.a in Cygwin

Rebase to 9.1

Rebase to 9.1