Port name unexpectedly handled case-sensitively when uninstalling

[ryandesign (Ryan Carsten Schmidt)]

Port names are supposed to be treated case-insensitively on the command line, but I encountered a situation where that didn't happen:

$ sudo port uninstall libunwind-headers libunwind pdal
--->  Unable to uninstall libunwind @5.0.1_0, the following ports depend on it:
--->  	PDAL @2.0.1_1
Error: Failed to uninstall libunwind: Please uninstall the ports that depend on libunwind first.

$ sudo port uninstall libunwind-headers libunwind PDAL
--->  Deactivating PDAL @2.0.1_1
--->  Cleaning PDAL
--->  Uninstalling PDAL @2.0.1_1
--->  Cleaning PDAL
--->  Deactivating libunwind @5.0.1_0
--->  Cleaning libunwind
--->  Uninstalling libunwind @5.0.1_0
--->  Cleaning libunwind
--->  Deactivating libunwind-headers @5.0.1_0
--->  Cleaning libunwind-headers
--->  Uninstalling libunwind-headers @5.0.1_0
--->  Cleaning libunwind-headers

[jmroot (Joshua Root)]

In 772a9ccaba5ae6417a12512669c3c061568a95b7/macports-base (master):

Use normalised port names in portlist_sortdependents

Closes: #60446