Added implementation of compressed trie, to be used soon
First foray into relocated symbol pointer copying.

dump_sym_names is a new function in tccelf.c that codifies what I
know about extracting pointers to globals, such as functions and
global variables, after the compiler state has run. My next step
will be to use this to build a trie mapping names to pointers, so
that I can store pointer addresses while deleting the tcc state.