Update stb_rect_pack.h to match dear-imgui (#2870)

dear-imgui updated the stb_rect_pack which bgfx should match.
Users with the old stb_rect_pack will get an assertion failure with font atlases not being packed properly with latest bgfx.

3rdparty/stb/stb_rect_pack.h

@@ -1,9 +1,19 @@
-// stb_rect_pack.h - v1.00 - public domain - rectangle packing
+// [DEAR IMGUI]
+// This is a slightly modified version of stb_rect_pack.h 1.01.
+// Grep for [DEAR IMGUI] to find the changes.
+// 
+// stb_rect_pack.h - v1.01 - public domain - rectangle packing
 // Sean Barrett 2014
 //
 // Useful for e.g. packing rectangular textures into an atlas.
 // Does not do rotation.
 //
+// Before #including,
+//
+//    #define STB_RECT_PACK_IMPLEMENTATION
+//
+// in the file that you want to have the implementation.
+//
 // Not necessarily the awesomest packing method, but better than
 // the totally naive one in stb_truetype (which is primarily what
 // this is meant to replace).
@@ -35,6 +45,7 @@
 //
 // Version history:
 //
+//     1.01  (2021-07-11)  always use large rect mode, expose STBRP__MAXVAL in public section
 //     1.00  (2019-02-25)  avoid small space waste; gracefully fail too-wide rectangles
 //     0.99  (2019-02-07)  warning fixes
 //     0.11  (2017-03-03)  return packing success/fail result
@@ -75,11 +86,10 @@ typedef struct stbrp_context stbrp_context;
 typedef struct stbrp_node    stbrp_node;
 typedef struct stbrp_rect    stbrp_rect;
 
-#ifdef STBRP_LARGE_RECTS
 typedef int            stbrp_coord;
-#else
-typedef unsigned short stbrp_coord;
-#endif
+
+#define STBRP__MAXVAL  0x7fffffff
+// Mostly for internal use, but this is the maximum supported coordinate value.
 
 STBRP_DEF int stbrp_pack_rects (stbrp_context *context, stbrp_rect *rects, int num_rects);
 // Assign packed locations to rectangles. The rectangles are of type
@@ -209,8 +219,10 @@ struct stbrp_context
 
 #ifdef _MSC_VER
 #define STBRP__NOTUSED(v)  (void)(v)
+#define STBRP__CDECL       __cdecl
 #else
 #define STBRP__NOTUSED(v)  (void)sizeof(v)
+#define STBRP__CDECL
 #endif
 
 enum
@@ -253,9 +265,6 @@ STBRP_DEF void stbrp_setup_allow_out_of_mem(stbrp_context *context, int allow_ou
 STBRP_DEF void stbrp_init_target(stbrp_context *context, int width, int height, stbrp_node *nodes, int num_nodes)
 {
    int i;
-#ifndef STBRP_LARGE_RECTS
-   STBRP_ASSERT(width <= 0xffff && height <= 0xffff);
-#endif
 
    for (i=0; i < num_nodes-1; ++i)
       nodes[i].next = &nodes[i+1];
@@ -274,11 +283,7 @@ STBRP_DEF void stbrp_init_target(stbrp_context *context, int width, int height,
    context->extra[0].y = 0;
    context->extra[0].next = &context->extra[1];
    context->extra[1].x = (stbrp_coord) width;
-#ifdef STBRP_LARGE_RECTS
    context->extra[1].y = (1<<30);
-#else
-   context->extra[1].y = 65535;
-#endif
    context->extra[1].next = NULL;
 }
 
@@ -424,7 +429,7 @@ static stbrp__findresult stbrp__skyline_find_best_pos(stbrp_context *c, int widt
             if (y <= best_y) {
                if (y < best_y || waste < best_waste || (waste==best_waste && xpos < best_x)) {
                   best_x = xpos;
-                  STBRP_ASSERT(y <= best_y);
+                  //STBRP_ASSERT(y <= best_y); [DEAR IMGUI]
                   best_y = y;
                   best_waste = waste;
                   best = prev;
@@ -520,7 +525,7 @@ static stbrp__findresult stbrp__skyline_pack_rectangle(stbrp_context *context, i
    return res;
 }
 
-static int rect_height_compare(const void *a, const void *b)
+static int STBRP__CDECL rect_height_compare(const void *a, const void *b)
 {
    const stbrp_rect *p = (const stbrp_rect *) a;
    const stbrp_rect *q = (const stbrp_rect *) b;
@@ -531,19 +536,13 @@ static int rect_height_compare(const void *a, const void *b)
    return (p->w > q->w) ? -1 : (p->w < q->w);
 }
 
-static int rect_original_order(const void *a, const void *b)
+static int STBRP__CDECL rect_original_order(const void *a, const void *b)
 {
    const stbrp_rect *p = (const stbrp_rect *) a;
    const stbrp_rect *q = (const stbrp_rect *) b;
    return (p->was_packed < q->was_packed) ? -1 : (p->was_packed > q->was_packed);
 }
 
-#ifdef STBRP_LARGE_RECTS
-#define STBRP__MAXVAL  0xffffffff
-#else
-#define STBRP__MAXVAL  0xffff
-#endif
-
 STBRP_DEF int stbrp_pack_rects(stbrp_context *context, stbrp_rect *rects, int num_rects)
 {
    int i, all_rects_packed = 1;