admesh: Fixed a problem in loading an STL when compiled with

Visual Studio 2013. Added multiple compile time checks for data
sizes and alignment. The library STL import is not big endian safe, so
added a test for endianity, modified STL export to a faster little endian only.

xs/src/admesh/stlinit.c

@@ -27,10 +27,8 @@
 
 #include "stl.h"
 
-#if !defined(SEEK_SET)
-#define SEEK_SET 0
-#define SEEK_CUR 1
-#define SEEK_END 2
+#ifndef SEEK_SET
+#error "SEEK_SET not defined"
 #endif
 
 void
@@ -277,10 +275,7 @@ stl_read(stl_file *stl, int first_facet, int first) {
       /* Read a single facet from a binary .STL file */
     {
       /* we assume little-endian architecture! */
-      if (fread(&facet.normal, sizeof(stl_normal), 1, stl->fp) \
-          + fread(&facet.vertex, sizeof(stl_vertex), 3, stl->fp) \
-          + fread(&facet.extra, sizeof(char), 2, stl->fp) != 6) {
-        perror("Cannot read facet");
+      if (fread(&facet, 1, SIZEOF_STL_FACET, stl->fp) != SIZEOF_STL_FACET) {
         stl->error = 1;
         return;
       }
@@ -343,8 +338,7 @@ stl_read(stl_file *stl, int first_facet, int first) {
     }
 #endif
     /* Write the facet into memory. */
-    stl->facet_start[i] = facet;
-
+    memcpy(stl->facet_start+i, &facet, SIZEOF_STL_FACET);
     stl_facet_stats(stl, facet, first);
     first = 0;
   }