use the destination filename as soname when provided when linking shared libraries

[donaldsonjw]

For example

bigloo -y -o libtest-1.0.so main.o

results in the soname being set to libtest-1.0.so instead of main.so as previously.

[manuel-serrano]

Hi Joe,

All my apologize for my slow reaction. I have merged your request now. Thank you very much.