Simplify some logic in parsing import libraries

Change struct used in export lookups

src/xenia/kernel/util/xex2.h

@@ -14,9 +14,6 @@
 #include "xenia/memory.h"
 
 namespace xe {
-namespace kernel {
-uint32_t xex2_get_header_size(const xex2_header* header);
-}  // namespace kernel
 }  // namespace xe
 
 typedef struct { int reserved; } xe_xex2_options_t;