checkpatch: patch to suit labwc coding style

checkpatch: patch to suit labwc coding style

Coding style specific changes include:

- Accept pango, glib and libxml2 CamelCase variables
- Remove "need consistent spacing around '*'" warning
- Do not warn about "structs that should be const"
- Do not warn on braces {} around single statements
- Do not warn about braces {} for single statement blocks
- Do not warn about wanting { on previous line for functions
- Remove check for missing blank line after declaration
- Ignore SPLIT_STRING COMPLEX_MACRO PREFER_KERNEL_TYPES
  LOGICAL_CONTINUATIONS PARENTHESIS_ALIGNMENT OPEN_ENDED_LINE
  MACRO_ARG_REUSE PREFER_FALLTHROUGH ARRAY_SIZE INITIALISED_STATIC

Other changes include:

- Do not complain about missing spelling.txt
- Print filename for each file, but no summary line