ghostscript: serialize raster integer parameters as signed

[victortrac]

Fixes #218.
Related to #222.

Problem

Commit b558b36 changed several Ghostscript CUPS raster parameters from
signed (%d) to unsigned (%u) formatting.

Some fields in cups_page_header_t are unsigned storage locations but
legitimately contain the two's-complement representation of signed values.
For example, label-printer PPDs use:

  <</cupsCompression -1>>setpagedevice

With libcupsfilters 2.2.1 this is emitted as:

  -dcupsCompression=4294967295

Ghostscript reads these device properties using its signed
param_read_int() interface, rejects the value, and terminates with:

  Error setting cupsCompression
  Unrecoverable error: rangecheck in .putdeviceprops

The same signedness problem affects cupsInteger[], as demonstrated by
issue #222.

Fix

Serialize CUPS raster integer fields using %d with an explicit (int)
conversion. This preserves signed values while avoiding the original
printf argument-type mismatch.

Reproduction

Environment:

• Arch Linux x86_64
• CUPS 2.4.19
• cups-filters 2.0.1
• libcupsfilters 2.2.1
• libppd 2.1.1
• Ghostscript 10.07.1
• 4BARCODE 4B-2054K using the standard ZPL rastertolabel PPD

Using the PPD default Darkness=-1:

• Unpatched 2.2.1:
  • emits -dcupsCompression=4294967295
  • exits with status 1
  • produces 0 raster bytes
• Patched 2.2.1:
  • emits -dcupsCompression=-1
  • exits with status 0
  • produces 500,340 raster bytes

The test invokes the universal filter directly with the same PPD and
input PDF, changing only the loaded libcupsfilters library.

Testing

• make check: 9 passed, 0 failed
• Arch package built successfully
• Direct unpatched/patched A/B rasterization test passed
• Live printing through the patched package succeeded

patched-2.2.1.log
unpatched-2.2.1.log