CLEANUP: include: tree-wide alphabetical sort of include files

This patch fixes all the leftovers from the include cleanup campaign. There
were not that many (~400 entries in ~150 files) but it was definitely worth
doing it as it revealed a few duplicates.
diff --git a/src/ebimtree.c b/src/ebimtree.c
index e6b82cc..1ac444a 100644
--- a/src/ebimtree.c
+++ b/src/ebimtree.c
@@ -20,8 +20,8 @@
 
 /* Consult ebimtree.h for more details about those functions */
 
-#include <import/ebpttree.h>
 #include <import/ebimtree.h>
+#include <import/ebpttree.h>
 
 /* Find the first occurrence of a key of <len> bytes in the tree <root>.
  * If none can be found, return NULL.