Release 0.7.3 "Perfume" - Mostly bug fixes

This release is mostly about bug fixes, improving the build on simulator, and accelerating the test suite while keeping it stable.

New features

• simulator: Add F8 key to save state in the simulator
• errors: Add a beep when an error is shown
• linux: Add -s option for screen scaling (when Qt gets scaling wrong)
• equations: Get library equation value for plotter, solver and integrator
• characters: Add constant, equation and lib markers to RPL menu
• characters: Add music-related characters and character menu
• commands: Add missing stack commands (nip, pick3, ndupn, unrot, unpick)

Bug fixes

• variables: Clone purged objects on stack after Purge
• units: unit * symbolic is preserved as is (e.g. 'A'_m)
• compare: Enforce the NumericalResults flag for comparisons
• constants: Fix parsing of constants, equations and library items
• sto: Repair file exists error storing to a source file
• simulator: Do not try to create directory if it exists
• Report file errors, e.g. permissions or I/O errors
• equations: Mark c and R as constants in equations
• simulator: Double clicks are now considered as virtual keyboard touches
• ui: Emit only one beep, not two, for a syntax error on the command line
• ui: Avoid rare null-dereference crash when menu label is not set
• complex: Report a syntax error if the second half is empty
• utf8: Do not accept constant/equation/library codepoint in names
• units: Multiplying by 1_m is OK even with algebraic
• tests: Avoid case where CLEAR does not clear errors
• audio: Improve audio reliability on the simulator
• linux: Rewrite the audio-generation code to avoid crashes
• linux: Avoid infinite recursion in the tests
• linux: Fix warnings about unused variables
• linux: Avoid warnings about null pointer in strcmp
• linux: Avoid build error due to bad ularge overload in settings
• linux: Fix type issue for the Insert function (reported as a warning)
• linux: Remove warning about mixing enums and integers
• linux: Avoid error on printf format
• linux: Avoid warnings about type qualifiers
• linux: Remove warnings about incompatible function casts
• linux: Address warnings about missing initializers
• linux: Fix warning about prinf formats
• linux: Address warning about signed vs unsigned
• linux: Remove warning about fall-through switch statement
• linux: Remove warnings about unused arguments
• tests: Repair several tests that were unstable due to scrolling images
• tests: Increase memory size to avoid occasional out of memory failures
• object: Make as_uint32 and as_uint64 consistent for negative input

Improvements

• ui: Emulate HP48/HP50G behavior for errors (do not require key to continue)
• simulator: Add I/O wrapper around file state save/restore
• dmcp: Remove double return in the code
• simulator: Accept numeric keys in DMCP menus
• doc: Add Kjell Christenson to list of authors
• tests: Run command-line tests silently
• tests: Clear settings the fast way for quick tests
• dmcp: Do not treat the buzzer as a recorder error (avoid message noise)
• simulator: Ensure error messages show up in a recorder dump
• tests: Increase memory size to avoid failing tests
• tests: Increase delay waiting for function plots to appear
• tests: Refactor test suite interaction with RPL thread to accelerate it
• tests: Add a delay before launching the test thread to load initial state
• tests: Add missing reference picture for char-menu