memleak in addition of strings

[ren]

Example:

string ab;
for (int i=0; i<10000; i++)
{
  ab = "a"+"b";  // note: the memleak still exists without the assignment
  memory(0);
}

This became very noticeable in a GIT-Fan computation, when we manipulated strings to write intermediate results to a file (which we ironically only did to keep the RAM usage low).

[hannes]

fixed with 76a7291160a6ba0f7e662bf112de635f35663c1d