Release 0.9.5 "Everlasting" - Power management, offline graphics

This release brings two major new features: vastly reduced power drain, and off-line persistent graphics.

New features

• Off-line graphics are the ability to draw images in memory instead of directly on screen. Like on HP calculators, this works by storing a graphic object in PICT. Unlike HP calculators, PICT is an actual variable in the current directory, meaning that you can have multiple PICT, although bitmaps use a lot of memory. For example, running 500 300 BLANK 'PICT' STO will create a 500x300 pixels off-line image in PICT, and all graphic commands after that will draw in that off-line image instead of on screen. Off-line graphics are not immediately shown on screen, but are displayed before returning to the command line in a way similar to the Show command (i.e. centererd if smaller than the screen, and with scrolling if larger). They are also persistent, meaning that you need to explicitly ClLCD to erase them.
• Add Blank, BlankGrob, BlankBitmap and BlankPixmap commands to create a blank image with default format, in HP GROB format, in DB48x bitmap (Black and white) format and in DB50x pixmap format (color RPL only).
• Add →HPGrob, →Bitmap, →Pixmap commands which can be used to generate an HP-compatible GROB format, a bitmap or a pixmap (color RPL only) from an object. If the object is already a graphic, perform conversion. Note that on color RPL, conversions between color and monochrome formats are supported. Colors are converted to monochrome using grayscale patterns.
• Add →LCD and LCD→ commands to send an object to the current graphics, or to create a graphic object from the current screen content.
• The Off command can now be used in a program and will preserve what is on screen. You can resume execution of the program by using the ON key. Add PowerOffWithImage command to show off-images even from programs.

Bug fixes

• Fix display of object Info in the interactive stack
• Clear system timers before entering system menu, so that the self test menu entry does not run a fast-paced loop.
• Fix off-by-one error in result of LastBitSet (number bits starting at 0)
• Correctly render color pixmaps when on the stack (color RPL only)

Improvements

• Reduce power usage dramatically by disabling timers when going to sleep. This manifests as a higher battery voltage being shown, which is closer to what the DM42 firmware or integrated self-test would show. This will most likely improve battery life for interactive uses of DB48x.
• Reorganize the MemoryMenu to make both GC and runtime statistics available
• Reorganize the GraphicsMenu by topics to accomodate the new commands
• Add image checks in the test infrastructure for RPL code examples
• Add tests for RGB colors
• Repair make compare which was trying to build a binary from compare.cc
• Make Sub a compatibility spelling for Extract, not the default one
• Adjust low battery indications to avoid premature warnings
• Make debug_printf use lower-level routines that can run earlier after boot
• Add make INSTALL_PGM_ONLY=y install option for faster install
• Generate DB48x bitmaps by default instead of HP-compatible GROBs. Bitmaps use less memory when the width is not a multiple of 8.
• Make test of pixel functions more reliable by increasing their timeout
• Add help for ModesMenu, SymbolicResults and NumericalResults