Fix memory leak and gcc4.4 compilation.
Fix memory leak and gcc4.4 compilation.

There was a small memory leak in parm_to_defparam_list where space for
"key" and "value" was being allocated via strdup and never freed.
This was fixed by freeing them at each return point.

In that function, key and value were defined to be const char* but
were later mutated.  gcc4.4 is more strict with const-ness in some
functions than previous versions (see
http://gcc.gnu.org/gcc-4.4/porting_to.html section "Strict
null-terminated sequence utilities"), so this caused compilation to
fail.  Fixed by removing the const modifier in the declaration of
those two variables and related nkey variable.  This also necessitated
malloc'ing room for value in one path through the code, which made
memory management easier as well.

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