Refactor app heap and memory boundary check, and fix os_printf compilation error (#356)

Insert app heap before __heap_base, or before new page
Fix os_printf compilation error in some platforms

core/shared/platform/linux/platform_init.c

@@ -16,3 +16,22 @@ bh_platform_destroy()
 {
 }
 
+int
+os_printf(const char *format, ...)
+{
+    int ret = 0;
+    va_list ap;
+
+    va_start(ap, format);
+    ret += vprintf(format, ap);
+    va_end(ap);
+
+    return ret;
+}
+
+int
+os_vprintf(const char *format, va_list ap)
+{
+    return vprintf(format, ap);
+}
+

core/shared/platform/linux/platform_internal.h

@@ -56,9 +56,6 @@ typedef pthread_mutex_t korp_mutex;
 typedef pthread_cond_t korp_cond;
 typedef pthread_t korp_thread;
 
-#define os_printf printf
-#define os_vprintf vprintf
-
 #if WASM_DISABLE_HW_BOUND_CHECK == 0
 #if defined(BUILD_TARGET_X86_64) \
     || defined(BUILD_TARGET_AMD_64) \