semihosting, plugin and doc updates:
- log a guest_error for failed semihosting open()
- clean up semihosting includes to reduce build duplication
- re-factor misc device initialisation to fail with &error_exit
- propagate Error * to gdbserver_start sub-functions
- fix 32-bit build of plugins and re-enable by default
- ensure IRQs don't preempt io recompiled instructions
- remove usage of gcc_struct to enable clang builds
- enable clang/lld to build plugins on windows
- various small kdoc typo fixes
- add perl scripts to editorconfig
- remove unused field from MemoryRegion
- make kdoc script a dependency so doc rebuilds get triggered
- expand developer documentation:
- notes on git-publish
- describe usage of b4
- setting up build dependencies
- codebase layout
- add a glossary of common terms
- optimise the windows ndis script