Makefile: Fix srcdir.
Revert rename from 5560eb5.
New pe_load_ext, an equivalent to pe_load with bitmasked options.
You can load a file and keep its stream open for further usage
by using pe_load_ext with option LIBPE_OPT_NOCLOSE_FD. Example:

	pe_ctx_t ctx;
	pe_err_e err = pe_load_ext(&ctx, "file.exe", LIBPE_OPT_NOCLOSE_FD);

You do NOT need to manually close the stream since pe_unload already
takes care of it.