Don't enable crashdumps by default. This build knob causes the build
to be done with debug symbols, which greatly increase the size of the
build, but this is all in vain because the executables and libraries
are subsequently stripped.

Build with debug symbols if WITH_DEBUG is set.

Build with -fstack-protector.

Only fetch unowinreg.dll when building the SDK.

Add three new options:

CRASHDUMP - Enable crashdumps, requires WITH_DEBUG

DBGUTIL   - Enable assertions, object counting, and other
            non-production runtime debugging.

DEBUG     - Compile with -O0 for better debugability.  The ports
            framework also sets WITH_DEBUG.

Fold a couple long lines in the Makefile.