xserver-xorg-video-vesa 1:2.6.0-1build1 FTBFS on armhf

[Benjamin Drung]

xserver-xorg-video-vesa 1:2.6.0-1build1 fails to build on armhf. Relevant log:

```
libtool: compile: gcc -DHAVE_CONFIG_H -I. -I../../src -I.. -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64 -D_TIME_BITS=64 -Wdate-time -D_FORTIFY_SOURCE=3 -I/usr/include/xorg -fvisibility=hidden -I/usr/include/pixman-1 -I/usr/include/X11/dri -I/usr/include/libdrm -g -O2 -Werror=implicit-function-declaration -ffile-prefix-map=/<<PKGBUILDDIR>>=. -fstack-protector-strong -Wformat -Werror=format-security -fno-stack-clash-protection -fdebug-prefix-map=/<<PKGBUILDDIR>>=/usr/src/xserver-xorg-video-vesa-1:2.6.0-1build1 -c ../../src/vesa.c -fPIC -DPIC -o .libs/vesa.o
../../src/vesa.c: In function ‘VESALoadPalette’:
../../src/vesa.c:1437:12: error: implicit declaration of function ‘outb’ [-Werror=implicit-function-declaration]
 1437 | outb(pVesa->ioBase + VGA_DAC_WRITE_ADDR, idx);
      | ^~~~
../../src/vesa.c:1431:18: error: implicit declaration of function ‘inb’ [-Werror=implicit-function-declaration]
 1431 | (void)inb(pVesa->ioBase + VGA_IOBASE_COLOR + VGA_IN_STAT_1_OFFSET); \
      | ^~~
../../src/vesa.c:1438:12: note: in expansion of macro ‘VESADACDelay’
 1438 | VESADACDelay();
      | ^~~~~~~~~~~~
```

[Benjamin Drung (bdrung)]

outb is defined in /usr/include/xorg/compiler.h guarded with some #ifdefs.