== DETAILS
This commit provides two tweaks:
1. Add the "library not found" error, value of -6, to the
`OSDynLoad_Error` enums
2. Define an `OSDynLoad_ExportType` enum and use it in place of the
`isData` boolean parameter to avoid raw `true`/`false` values in the
code and make usages easier to read:
```c
// before - unclear what "false" means in this context
last_error = OSDynLoad_FindExport((OSDynLoad_Module)lib, false, proc, &ptr_sym);
```
vs:
```c
// after - aha, we're looking up a function symbol
last_error = OSDynLoad_FindExport((OSDynLoad_Module)lib, OS_DYNLOAD_EXPORT_FUNC, proc, &ptr_sym);
```
RPL files are shared libraries (like a .dll file), as opposed to the RPX
files which are executables (like a .exe file).
Use rpl_main as defined in dynload.h like one would DllMain on Windows.
