Fix the legacy makefile builds on ARM, MIPS and PowerPC, where
hardware-optimized compilation was enabled by default in the generic
source files, but without including the machine-specific source files.
Delete scripts/makefile.linux-opt.
Considering that "-Wextra" is a more descriptive alternative to "-W",
and that "-Wundef" is a highly useful warning option that has been
available in ancient versions of gcc (version 2.x), we replace all
occurrences of "-W -Wall" with "-Wall -Wextra -Wundef".
Also clean up the makefiles.
Delete variables (ALIGN, ARCH, DOCS) and targets (writelock) that are
no longer necessary.
Reorder the object file lists alphabetically, consistently across all
makefiles and build scripts.
Apply other minor fixes.
