tiny C support; cosmetic improvements for the docs

tinyc/lib/alloca86.S

@@ -0,0 +1,33 @@
+/* ---------------------------------------------- */
+/* alloca86.S */
+
+#include "../config.h"
+
+.globl alloca
+
+alloca:
+    pop     %edx
+    pop     %eax
+    add     $3,%eax
+    and     $-4,%eax
+    jz      p3
+
+#ifdef TCC_TARGET_PE
+p1:
+    cmp     $4096,%eax
+    jle     p2
+    sub     $4096,%esp
+    sub     $4096,%eax
+    test    %eax,(%esp)
+    jmp p1
+p2:
+#endif
+
+    sub     %eax,%esp
+    mov     %esp,%eax
+p3:
+    push    %edx
+    push    %edx
+    ret
+
+/* ---------------------------------------------- */