Keep the existing MARS debug logging switch separate from compiler
debug flags. ENABLE_DEBUG still controls the legacy DO_DEBUG/XDPRINTF
code paths, while the new ENABLE_DEBUG_BUILD option enables a real
debug build with -g3, -O0 and -fno-omit-frame-pointer.
When ENABLE_DEBUG_BUILD is set on single-config generators, CMake also
forces CMAKE_BUILD_TYPE=Debug so gdb/valgrind builds can be enabled
without manually passing compiler flags.
Add a FindQuota.cmake module that checks for the Linux quota headers and
symbols required by the MARS NWE quota backend. Prefer modern
<sys/quota.h> with quotactl(), and keep <linux/quota.h> as fallback for
older systems.
Enable quota support by default, but only compile it in when the required
headers and quota symbols are available. Also move the QTAINSYS define to
the detected sys/quota.h path so modern Linux builds use the correct
header automatically.
