* Prevent libcurl from inadvertently being initialized twice.
* Dynamically load libcurl only when required.
* Reduce the number of worker threads when loading footprint libraries to
prevent issues with the GitHub plugin.
* Fix unitialized variable in MSG_PANEL_ITEM default ctor.
* Fix a bunch of uncaught exception issues.
* Fix a memory leak in the NETLIST_READER::GetNetlistReader() when an
an attempt to read an invalid net list file occurs.
comment for GITHUB_PLUGIN which should flow into Doxygen output.
*) Rewrote:
PCB_BASE_FRAME::Save_Module_In_Library(): now uses fp-lib-table and PROPERTIES.
PCB_EDIT_FRAME::ArchiveModulesOnBoard(): now can archive to any writable library type.
PCB_BASE_FRAME::SelectLibrary(): is now generic for selecting a library, not just the active library.
*) Move button handlers to LEFT MOUSE CLICK from COMMAND events, so wxGrid focus is not lost.
*) Sketch out the concept of COW support for the GITHUB_PLUGIN in its @todo.