Perform readlink on /proc/self/exe.

This fixes an error where java would do readlink("/proc/self/exe") but
would wrongly get a path to a symlink back. e.g. on my Arch Linux system:

$ ls -lha /usr/bin/java
lrwxrwxrwx 1 root root 40 Jun 14 08:25 /usr/bin/java -> /usr/lib/jvm/java-7-openjdk/jre/bin/java

and on our RHEL6:

$ ls -lha /usr/bin/java
lrwxrwxrwx 1 root root 22 Apr  5 19:01 /usr/bin/java -> /etc/alternatives/java

So, after doing readlink("/proc/self/exe"), it would get back "/usr/bin/java", which would break
library search later on:

parrot_run -- /usr/bin/java -version
/usr/bin/java: error while loading shared libraries: libjli.so: cannot open shared object file: No such file or directory

This is probably unrelated to #502.