loci: optimize loci.c for size

Reduces the size of loci.o by 27%.
diff --git a/c_gen/c_code_gen.py b/c_gen/c_code_gen.py
index b32bd27..52d30f2 100644
--- a/c_gen/c_code_gen.py
+++ b/c_gen/c_code_gen.py
@@ -756,6 +756,8 @@
  *
  ****************************************************************/
 
+#pragma GCC optimize ("s")
+
 #include <loci/loci.h>
 #include <loci/of_object.h>
 #include "loci_log.h"