Delete all SPARC optimizations

SPARC has been obsolete for a long time and makes little sense as a
H.264 encoding platform.

Also update authors file.
build: Add dependencies on x86inc.asm/x86util.asm for all .asm files

This is a little bit overzealous, but errs on the side of caution.
Generating full dependency information is also possible, but slightly
slows down the build as YASM cannot do it as a sideeffect of compilation.
configure: Drop workaround for obsolete gcc 4.2 on ARM
build: Simplify phony target declaration with wildcards
build: Replace cltostr.pl by a shell script

This avoids a dependency on Perl to build OpenCL support.
configure: Add -Wno-maybe-uninitialized to CFLAGS

The warnings generated by -Wmaybe-uninitialized are mostly spurious.