A little fleshing out of the dynamic library header

[gblues]

== 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:

   // before - unclear what "false" means in this context
   last_error = OSDynLoad_FindExport((OSDynLoad_Module)lib, false, proc, &ptr_sym);

   vs:

   // after - aha, we're looking up a function symbol 
   last_error = OSDynLoad_FindExport((OSDynLoad_Module)lib, OS_DYNLOAD_EXPORT_FUNC, proc, &ptr_sym);

[Maschell]

Where is that -6 coming from? decaf defines ModuleNotFound as 0xBAD10023. It's probably a good idea to add the missing enum values from decaf to wut

[gblues]

The -6 comes from my own experiments trying to use OSDynload_Acquire() with WUT-built RPLs, and I poked around via Ghidra to see the context of the -6 return code.