Major changes on the 8514/A side again (March 30th, 2025)

1. The DX/DY coordinates for BitBLT are now signed again, fixes 8514/A cursor issues.
2. Made the busy/data available processor statuses more like the ATI one for more stability and no stalls, fixes Windows 3.x and IBM OS/2 1.x (possibly later ones too) that use the built-in 8514/A driver.
3. Made the mode switching clearer (through a note) regarding the shadow sets, this should make every program happy, I hope.
4. In the Mach32 series only, a first load of the CRT sets also initializes the GE offsets if the corresponding bit is set, fixes Mach8/32 mode tests in their eeprom and demoai with hdiload from ATI/IBM.

src/include/86box/vid_8514a.h

@@ -92,8 +92,8 @@ typedef struct ibm8514_t {
         uint16_t advfunc_cntl;
         uint16_t cur_y;
         uint16_t cur_x;
-        uint16_t destx;
-        uint16_t desty;
+        int16_t  destx;
+        int16_t  desty;
         int16_t  desty_axstp;
         int16_t  destx_distp;
         int16_t  err_term;

src/include/86box/vid_ati_mach8.h

@@ -77,7 +77,8 @@ typedef struct mach_t {
     uint8_t overscan_g_col_24;
     uint8_t overscan_r_col_24;
     uint16_t fifo_test_data[17];
-    int resolution_crt;
+    int port_len;
+    int crt_resolution;
 
     struct {
         uint8_t  line_idx;