[Feat] (MG_Impl/GLImpl, MG_State): implement glHint, glPointParameter*, glPixelStoref, glGetDoublev

Six pure-state entry points that were stubs or empty // TODO bodies, all backed by new
context state and read back through glGet*.

* glHint: Hint_State was an empty TODO. Store the 4 GL 3.3 core hint targets (LINE_SMOOTH,
  POLYGON_SMOOTH, TEXTURE_COMPRESSION, FRAGMENT_SHADER_DERIVATIVE), default GL_DONT_CARE.
  Validate target and mode (FASTEST/NICEST/DONT_CARE) -> GL_INVALID_ENUM otherwise. The
  compatibility-only targets (GL_PERSPECTIVE_CORRECTION_HINT, GL_POINT_SMOOTH_HINT, GL_FOG_HINT,
  GL_GENERATE_MIPMAP_HINT) are rejected. The glGetIntegerv hint cases, previously hardcoded to
  GL_DONT_CARE, now read the stored value; glGetBooleanv on a hint is always GL_TRUE.

* glPointParameter{f,i,fv,iv}: the scalar _State bodies were empty TODOs and the *v forms were
  stubs. Only the 2 core pnames are accepted: GL_POINT_FADE_THRESHOLD_SIZE (float, default 1.0,
  GL_INVALID_VALUE if negative) and GL_POINT_SPRITE_COORD_ORIGIN (GL_LOWER_LEFT/GL_UPPER_LEFT,
  default GL_UPPER_LEFT, GL_INVALID_ENUM on a bad value -- note the different error code from the
  fade case). The compat pnames (POINT_SIZE_MIN/MAX, POINT_DISTANCE_ATTENUATION) are rejected. All
  four forms funnel through one (pname, float) handler. glGetIntegerv(GL_POINT_FADE_THRESHOLD_SIZE)
  was hardcoded to 1; it now rounds the stored float, glGetFloatv reads the float directly (keeping
  the fractional part), and GL_POINT_SPRITE_COORD_ORIGIN gained a getter case (it had none).

* glPixelStoref: funnels into the existing glPixelStorei state, but converts per type -- boolean
  pnames (PACK/UNPACK_SWAP_BYTES/LSB_FIRST) by a zero-test so 0.4 -> TRUE, integer pnames by
  round-to-nearest. A blanket round would wrongly turn a fractional true flag into false.

* glGetDoublev: funnels through glGetFloatv and widens, writing exactly the pname's component count
  (1/2/4) so a single-component query cannot overrun the caller's buffer. MobileGL stores no native
  double state (depth range/clear are float), so widening from float matches its real resolution.

State added to RenderStateParameters + RenderState Set/Get + GLContext wrappers, following the
existing LineWidth/DepthRange pattern. Covered by 4 SanityTest cases (set-then-get round trips, the
core-vs-compat enum rejections, the two different error codes, and the glPixelStoref boolean
zero-test, which was verified to fail against a blanket-round implementation).

MobileGL/MG_State/GLState/RenderState/RenderState.h

@@ -250,6 +250,16 @@ namespace MobileGL {
         FrontFaceMode FrontFaceModeSetting = FrontFaceMode::CounterClockwise;
         ProvokingVertexMode ProvokingVertexModeSetting = ProvokingVertexMode::LastVertex;
 
+        // Hints (glHint). All GL 3.3 core hint targets default to GL_DONT_CARE.
+        GLenum LineSmoothHint = GL_DONT_CARE;
+        GLenum PolygonSmoothHint = GL_DONT_CARE;
+        GLenum TextureCompressionHint = GL_DONT_CARE;
+        GLenum FragmentShaderDerivativeHint = GL_DONT_CARE;
+
+        // Point parameters (glPointParameter). Only the two GL 3.3 core pnames.
+        Float PointFadeThresholdSize = 1.0f;
+        GLenum PointSpriteCoordOrigin = GL_UPPER_LEFT;
+
         // Scissor
         Bool ColorLogicOpEnabled = false;
         Bool DebugOutputEnabled = false;
@@ -293,6 +303,13 @@ namespace MobileGL {
                 void SetPolygonOffset(Float factor, Float units);
                 Float GetPolygonOffsetFactor() const;
                 Float GetPolygonOffsetUnits() const;
+                // Hints. target must be one of the 4 GL 3.3 core hint targets (validated by the caller).
+                void SetHint(GLenum target, GLenum mode);
+                GLenum GetHint(GLenum target) const;
+                void SetPointFadeThresholdSize(Float size);
+                Float GetPointFadeThresholdSize() const;
+                void SetPointSpriteCoordOrigin(GLenum origin);
+                GLenum GetPointSpriteCoordOrigin() const;
 
                 // Capabilities
                 void SetCapability(CapabilityInput cap, Bool enabled);