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anyio: Add --device AUTO and --device SPI

Fix -Wformat= warnings

Testing performed:  Both found an attached SPI device on a Pi4 e.g.,

    $ ./mesaflash --device auto --addr /dev/spidev0.0 --spi --readhmid | head -1
    unable to set bpw32, fallback to bpw8
    Configuration Name: HOSTMOT2

Mostly, this involves using the "z" length modifier where a sizeof() is involved

hostmot2.c:50:20: warning: ‘hm2_get_pin_secondary_name’ defined but not used [-Wunused-function]
 static const char* hm2_get_pin_secondary_name(hm2_pin_desc_t *pin) {
                    ^~~~~~~~~~~~~~~~~~~~~~~~~~

Allow to pass VERSION string from the build system

Usage:
  $ CFLAGS='-DVERSION=\"version-string\"' make

Signed-off-by: Damian Wrobel <dwrobel@ertelnet.rybnik.pl>

This fixes a lintian warning.

This is needed for older compilers (like Wheezy's gcc 4.7.2 and Jessie's
gcc 4.9.2) to accept "modern" things like for-loops with the index
variable declared in them:

hostmot2.c:759:5: error: 'for' loop initial declarations are only allowed in C99 or C11 mode
     for (int i = 0; i < num_pins; i ++) {
      ^
hostmot2.c:759:5: note: use option -std=c99, -std=gnu99, -std=c11 or -std=gnu11 to compile your code

This also means we no longer need to override CFLAGS in the travis config.

Make sure the requested filename fits in the `bitfile_name` buffer before
copying it.