ddebug: use util_snprintf() in dd_get_debug_filename_and_mkdir

Instead of plain snprintf(). To fix the MSVC 2013 build:

  Compiling src\gallium\auxiliary\driver_ddebug\dd_draw.c ...
dd_draw.c
c:\projects\mesa\src\gallium\auxiliary\driver_ddebug\dd_util.h(60) : warning C4013: 'snprintf' undefined; assuming extern returning int

...

gallium.lib(dd_draw.obj) : error LNK2001: unresolved external symbol _snprintf
build\windows-x86-debug\gallium\targets\graw-gdi\graw.dll : fatal error LNK1120: 1 unresolved externals
scons: *** [build\windows-x86-debug\gallium\targets\graw-gdi\graw.dll] Error 1120
scons: building terminated because of errors.

Fixes: 6ff0c6f4 ("gallium: move ddebug, noop, rbug, trace to auxiliary to improve build times")
Cc: Marek Olšák <marek.olsak@amd.com>
Cc: Brian Paul <brianp@vmware.com>
Cc: Roland Scheidegger <sroland@vmware.com>
Cc: Nicolai Hähnle <nicolai.haehnle@amd.com>
Signed-off-by: Andres Gomez <agomez@igalia.com>
Reviewed-by: Brian Paul <brianp@vmware.com>
Reviewed-by: Nicolai Hähnle <nicolai.haehnle@amd.com>
(cherry picked from commit 1090e97e)