Rename BindingsSpec into StdLib spec, add more bindings

[markehammons]

BindingsSpec is really a test of stdlib.h bindings, so lets make it official. Rename BindingsSpec to StdlibSpec and add bindings for the following:

• [x] atof
• [ ] atoi
• [ ] atol
• [ ] atoll
• [x] strtod
• [ ] strtof
• [ ] strtol
• [ ] strtold
• [ ] strtoll
• [ ] strtoul (dependent on #12)
• [ ] strtoull (dependent on #12)
• [ ] srand
• [ ] calloc
• [ ] free
• [ ] malloc
• [ ] relalloc
• [ ] getenv
• [ ] bsearch
• [ ] ldiv
• [ ] llabs
• [ ] lldiv

[markehammons]

Thank @rrramiro for adding bindings to atof and strtod, as well as your hard work implementing Mem.readAddress!