Add lm_symbol_t type

[rdbo]

There should be a lm_symbol_t type, something like this:

typedef struct {
        lm_cstring_t name;
        lm_address_t value;
} lm_symbol_t;

[rdbo]

Not a good idea: the symbol name is deleted after the callback finishes

[rdbo]

This might be a good idea, as long as only LM_EnumSymbols uses the lm_symbol_t type, because then you can just pass the pointer to the symbol to it and everything is still fine. On the other hand, LM_FindSymbol should not use lm_symbol_t because the lm_cstring_t name field is going to be deleted eventually.

[rdbo]

Done: 2ef08fce4691d13b5b06a1226dfbcb1ebf6c4028