Fix symlink resolution in run-sbcl.sh

[Stelian Ionescu]

run-sbcl.sh fails to start when being executed via a symlink because it first computes the directory of argv[0] which it then resolves instead of doing it in the opposite order(first resolve argv[0] then compute the containing directory to find the source tree). Furthermore, it uses «readlink -f» which is not available on OSX.

[Stelian Ionescu (sionescu)]

The attached patch uses the POSIX tool expr to resolve symlinks in a portable fashion. It also replaces the use of $* with $@ because $* should never be used since it causes problems with arguments containing spaces. The idiom «"$@"» is equivalent to "$1" "$2" ..., i.e. APPLY.

[Stelian Ionescu (sionescu)]

I have tested that the patch works on Linux and OSX, but not Cygwin.