Everywhere: Give stbtt its own 32MB static memory pool

At boot time, we preallocate 32MB of RAM to reuse for all malloc()
requests by stbtt_RenderText(), which should be more than enough for the
primary use case (browsing web pages).

System/FFI/TrueType.HC

@@ -0,0 +1,31 @@
+U64 stbtt_heap = MAlloc(1048576 * 32);
+U64 stbtt_pos = 0;
+
+U64 @stbtt_malloc(I64 size)
+{
+    //"stbtt_malloc(%d)\n", size;
+    U64 ptr = stbtt_heap + stbtt_pos;
+    stbtt_pos += size;
+    return ptr;
+}
+
+U0 @stbtt_free(U8* ptr)
+{
+    //"stbtt_free(0x%08x)\n", ptr;
+}
+
+U0 _Z15truetype_malloci()
+{
+    PUSH_SYSV_REGS
+    GET_SYSV_ARGS
+    @stbtt_malloc(p0);
+    POP_SYSV_REGS
+}
+
+U0 _Z13truetype_freePv()
+{
+    PUSH_SYSV_REGS
+    GET_SYSV_ARGS
+    @stbtt_free(p0);
+    POP_SYSV_REGS
+}

System/Libraries/Graphics2D.HC

@@ -1206,7 +1206,7 @@ I64 @get_truetype_baseline(U8* font_name, I64 size)
     dc->width -= 16;
     dc->height -= size / 4;
     res = Y2Pos(dc);
-    DCDel(dc);
+    Free(dc);
     return res;
 }
 
@@ -1232,7 +1232,7 @@ U0 Text2D(Context2D* ctx, U8* font_name, I64 x, I64 y, I64 size, U32 color, U8*
     }
     BlendRect2D(text_ctx, ctx);
     DelContext2D(text_ctx);
-    DCDel(dc);
+    Free(dc);
 }
 
 Context2D* FastBoxBlur2D(Context2D* img, I64 radius)

System/MakeSystem.HC

@@ -23,6 +23,7 @@ WinToTop(adam_task);
 #include "FFI/LibC";
 #include "FFI/New";
 #include "FFI/ELF64";
+#include "FFI/TrueType";
 
 // stb_image library
 #include "Utilities/Image";

System/Utilities/TrueType.HC

@@ -44,6 +44,7 @@ U8* @stbtt_RenderText(stbtt_fontinfo* info, I32 b_w, I32 b_h, I32 l_h, I32* word
     U64 reg R8 r8 = word;
     U64 reg R9 r9 = advance;
     no_warn rdi, rsi, rdx, rcx, r8, r9;
+    stbtt_pos = 0;
     asm {
         MOV RAX, STBTT_RENDERTEXT
         CALL RAX