Make error message in require more descriptive for custom LOVE library loader.

[MikuAuahDark]

This PR adds paths that LOVE tried to load when require fails in the error message.

The new output will look like this:

Error

main.lua:1: module 'path.to.module' not found:
no field package.preload['path.to.module']
no 'path/to/module' in LOVE game directories:
  tried 'path/to/module.lua'
  tried 'path/to/module/init.lua'
no file 'path/to/module' in LOVE paths:
  tried 'path/to/module.dll' in save directory
no file '.\path\to\module.lua'
no file 'D:\Data\Development\love-dev\install-11\lua\path\to\module.lua'
no file 'D:\Data\Development\love-dev\install-11\lua\path\to\module\init.lua'
no file '.\path\to\module.dll'
no file 'D:\Data\Development\love-dev\install-11\path\to\module.dll'
no file 'D:\Data\Development\love-dev\install-11\loadall.dll'
no file '.\path.dll'
no file 'D:\Data\Development\love-dev\install-11\path.dll'
no file 'D:\Data\Development\love-dev\install-11\loadall.dll'

Fixes #1864

[slime73]

I think this isn't guaranteed to only look (or work) in the save directory right now, especially if love 12's new mount APIs have been used.

[MikuAuahDark]

What would be a good replacement text for those?

[slime73]

Maybe it could be something like this for the Lua loader:

No Lua code 'path/to/module' in LOVE filesystem paths:
  tried 'path/to/module.lua'

And for the C module loader:

No C library 'path/to/module' in LOVE filesystem paths:
  tried 'path/to/module.dll'

Does that make sense? I haven't thought about this too hard. Maybe the language could still be tweaked a bit...

[MikuAuahDark]

For the C module paths, I was thinking of resolving the fullpath then printing the absolute path, but then I realize PHYSFS_getRealDir only works when the file is there (which most likely succeeded when this codepath is reached, defeating the purpose).