exercise package-building

Fix compiler diagnostics etc

This fixes a diagnostic seen on Ubuntu 10.04 building the examples:

converting a packed 'opd_mode_1_7i77_t' {aka 'struct
opd_mode_1_7i77_struct'} pointer (alignment 1) to a 'u32' {aka 'unsigned int'}
pointer (alignment 4) may result in an unaligned pointer value
[-Werror=address-of-packed-member]

Remove files needed only for Windows

Add daughterboard hints to improve readhmid output

pci_boards: Enable the board before mmap'ing it

This fixes a problem where it was necessary to run linuxcnc first, before
running mesaflash.  This seemed not to affect standard PCs but affected the
CM4.

This can be used to improve the output of `--readhmid` by specifying
daughtercards that are attached at each header.

For example, `mesaflash --device 5i25 --dbname1 7i76`

I asked Peter whether building mesaflash on Windows was important to him, and
he said he has not used it for a long time.

I don't like carrying these files, especially the binary files without clear
links to their source.  So let's remove them.

(These files also wouldn't be suitable for modern 64-bit versions of Windows,
which would be virtually any current system.)

.. this simplifies error checking, and fixes a diagnostic about
comparing signed and unsigned numbers.

.. mostly by hinting to the compiler that they are intended to be
unused.

Enable PCI device enumeration on Compute Module 4

 * The PCI offset may be a 64-bit number like 0x600000000, which needs
   to fit in off_t (for mmap) and board_struct.mem_base
 * off_t is only 64-bits with -D_FILE_OFFSET_BITS=64
   (which is not the default in 2021!!!)
 * This requires the offset to be printed as a uint64_t
 * mmap was not checked for failure

After this change, I can detect a 5i24 plugged into the 1x slot of
a Raspberry Pi Compute Module 4 IO board with 2GB RAM compute module.
That's the only operation I tried.

Make PCI & EPP support conditional

This should fix compilation on aarch64.

Adds Sigma 5 Encoder GTAGs

Add build-essential to install list

Add mesaflash availability info on Fedora