[N-Gage] Remove optimisations except for native texture handling prior to some rework of the rendering back-end

[N-Gage] Set proper brush style to draw filled rects properly.

[N-Gage] Add persistent buffers to avoid per-frame memory allocations (which are expensive)

[N-Gage] Add support for SDL_TEXTURE_ACCESS_TARGET, fixes #13165

[N-Gage] Update README, add hint that the compiler does not support aggregate initializations for structs (knowing this, avoids a lot of headache during debugging)

[N-Gage] Add basic fast-path optimisations for render operations.

[N-Gage] Fix line drawing.

docs/README-ngage.md

@@ -33,14 +33,6 @@ software renderer has been removed.
 The outcome is a significantly leaner and more efficient SDL port, which we hope
 will breathe new life into this beloved yet obscure platform.
 
-## To the Stubborn Legends of the DC Scene
-
-This port is lovingly dedicated to the ever-nostalgic Dreamcast homebrew scene --
-because if we managed to pull this off for the N-Gage (yes, the N-Gage), surely
-you guys can stop clinging to SDL2 like it's a rare Shenmue prototype and finally
-make the leap to SDL3.  It's 2025, not 1999 -- and let's be honest, you're rocking
-a state-of-the-art C23 compiler.  The irony writes itself.
-
 ## Existing Issues and Limitations
 
 - For now, the new
@@ -62,3 +54,6 @@ a state-of-the-art C23 compiler.  The irony writes itself.
  expected to be resolved in a future update.
 
 - Dependency tracking is currently non-functional.
+
+- The compiler doesn't support aggregate initialization for structs, so
+  each field must be assigned explicitly.