0.7.0 - time value of money (TVM); multiple BASE word sizes

• 0.7.0 (2023-11-20)
  • STAT
    • fix broken Sigma+ and Sigma- when Y==0
    • use alternate equation for SLOP (slope) which works when the Y
      data points are the same
    • fix "stack lift disable" feature of Sigma+ and Sigma- which
      probably got broken during an earlier refactoring
    • check for division by zero when calculating weighted mean WMN, and
      show 9.9999999999999E99 to indicate error, allowing weightedX (or
      weightedY) to be evaluated even if the other is undefined
  • BASE
    • implement WSIZ (set word size) restricted to 8, 16, 24, and 32
      (inspired by HP-16C and Free42)
    • display appropriate number of digits for various WSIZ values, for
      various base modes (HEX, OCT, BIN)
    • display ellipsis character on left most digit in BIN mode if
      the binary number cannot be fully displayed using 14 digits on the
      screen
    • Breaking Change: change order of BDIV results in X and Y
      registers
      • now X=quotient=Y/X and Y=remainder=Y%X
      • allows easier recovery of original X using LastX *
  • MATH: add LN1+, E^X-
    • implement log(1+x) and e^x-1 respectively
    • more accurate than their naive implementations when x is close to 0
    • use mathematical identities involving hyperbolic sinh() and
      asinh() functions to avoid roundoff errors
  • TVM
    • add TVM (time value of money) submenu hierarchy (inspired by HP-12C
      and HP-30b)
    • implement relatively simple Newton-Secant root solver to calculate
      the I%YR from the other 4 TVM variables
    • significant performance and robustness improvements can probably be
      made in the future
  • add storage register arithmetic operations
    • STO+, STO-, STO*, STO/
    • RCL+, RCL-, RCL*, RCL/
  • convert to multi-page flash application
    • now consumes 2 flash pages (2 x 16 kiB)
  • CLEAR multiple times to clear RPN stack
    • If CLEAR is pressed on an empty edit line (just a _ cursor), then
      the message "CLEAR Again to Clear Stack" will be displayed.
    • If CLEAR is pressed again right after this message, the RPN stack is
      cleared, invoking the ROOT > CLR > CLST menu function.
    • Provides a quick shortcut to the CLST function which can be
      difficult to reach when the current menu item is deeply nested in
      another part of the menu hierarchy.
    • The TI-OS does not support 2ND CLEAR, it returns the same keycode as
      CLEAR. So invoking CLST on multiple CLEAR presses seemed like
      the most reasonable workaround.
  • implement jumpBack for MODE button shortcut
    • When ROOT > MODE is reached through the hierchical menu, the
      ON/EXIT/ESC button goes back up the menu hierarchy to the parent,
      the ROOT.
    • When ROOT > MODE is invoked through the MODE button on the
      keyboard, the ON/EXIT/ESC button jumps back to the previous menu
      location, instead of going back up the menu tree.
    • This allows quick changes to the FIX, SCI, and ENG display
      modes, without losing one's place in the menu hierarchy.
  • fix incorrect handling of DEL after a FIX, SCI, or ENG mode
    • when the DEL (backspace) button is pressed after a 2-digit argument
      of a FIX (or SCI etc), one of the digits of the 2-digit argument
      remained in the input buffer
    • the fix now correctly clears the input buffer when transitioning into
      edit mode from a normal mode
  • Potential Breaking Change: STO, RCL, FIX, SCI, ENG argument
    prompt is no longer saved and restored on QUIT or OFF
    • a new Command Arg parser was required to support storage register
      arithmetics
    • it uses a secondary GetKey() parsing loop which implements its own
      2ND QUIT and 2ND OFF handlers
    • the state of the secondary GetKey() parsing loop is not saved and
      restored