Change code and naming style, fix several bugs, removed math types.

After a while I felt that putting underscores between words was not the
best solution, so I changed the underscores to capital letters.

Fixed consistency bug between POSIX/Win32 platform in BH_FileOpen.

Removed definitions for math types (vector, matrix, etc.) due to
potential aliasing issues.

main.c

@@ -2,9 +2,10 @@
 
 int main()
 {
-    bh_io_t *io = bh_file_new("hello.txt");
-    bh_io_open(io, BH_IO_WRITE);
-    bh_io_write(io, "Hello, world!", 13, NULL);
-    bh_io_free(io);
+    BH_IO *io = BH_FileNew("hello.txt");
+    BH_IOOpen(io, BH_IO_WRITE);
+    BH_IOWrite(io, "Hello, world!", 13, NULL);
+    BH_IOFree(io);
+
     return 0;
 }