Centrally manage ASM version in parent POM

Centrally manage ASM version in parent POM

There is a warning because 'asm-renamed' uses
<version>${asm.version}</version> in its artifact descriptor instead of
a fixed version. but as long as Maven still permits it, let us use it
this way. Flatten Maven plugin replaces it by a resolved number anyway
for the dependency-reduced POM.

Signed-off-by: Alexander Kriegisch <Alexander@Kriegisch.name>