fix: add missing CS renderer struct members for Linux builds (#1596)

[luckyseoul]

Summary

Fixes #1596 (Debian 13 / source build failure in the OpenGL compute-shader path).

vidcs.c already assigns and reads fields that were never declared on the shared types, so compilers error with has no member named 'userclipMode', bitmap_base, bitmap_wrap_size, sprite_rgb_priority_per_line, and msb_shadow_enabled_per_line.

This PR adds the missing members (with init for userclipMode) and a small compile/run test that exercises those real header fields.

Hardware / docs grounding

Field	Role	Manual
Vdp1.userclipMode	Latched CMDPMOD Cmod (bit 9) on user-clipping commands: 0 = inside drawing, 1 = outside drawing	ST-013 VDP1 User's Manual §6.3 CMDPMOD (ST-013-R3-061694.pdf)
vdp2draw_struct.bitmap_base / bitmap_wrap_size	Bitmap NBG VRAM window for wrapped cell fetch	ST-058 VDP2 User's Manual (ST-058-R2-060194.pdf)
Ygl.sprite_rgb_priority_per_line	When SPCLMD selects RGB sprites, priority from PRISA reg 0	ST-058 sprite control / priority
Ygl.msb_shadow_enabled_per_line	MSB shadow when SPWINEN=0 and sprite type 2–7	ST-058 shadow / SPCTL

Local archive paths used while developing:

• saturn-docs/files/ST-013-R3-061694.pdf
• saturn-docs/files/ST-058-R2-060194.pdf

Test plan

• Reproduced Fails to build from source on Debian 13 #1596 member-missing errors before the fix (compile of test against unfixed headers)
• After fix: make -f Makefile.cs_struct_members in yabause/src/tests → PASS (or compile cs_struct_members_test.c with the include flags in that Makefile)
• Full Qt/SDL Kronos link build on a machine with SDL2/Qt5/GLFW deps
• Optional: in-emulator check that user-clip outside mode still latches from CMDPMOD

Notes

• userclipMode is software latched state alongside the existing userclipX/Y fields (same pattern as other command-derived VDP1 state).
• Full-tree cmake on the contributor host was blocked by missing libsdl2-dev/glfw3; verification used the focused header test that hits the same symbols vidcs.c requires.