Fix type of bit values (fixes compiler warning)

A single bit cannot represent a signed integer value, so it must be an
unsigned integer. This fixes a compiler warning:

    In file included from ../ccutil/clst.h:24:0,
                     from ../ccstruct/blobbox.h:23,
                     from workingpartset.h:24,
                     from workingpartset.cpp:21:
    ../ccstruct/blobbox.h: In member function ‘void BLOBNBOX::set_reduced_box(TBOX)’:
    ../ccutil/host.h:79:25: warning: overflow in conversion from ‘int’ to ‘signed char:1’ changes value from ‘1’ to ‘-1’ [-Woverflow]
     #define TRUE            1
                             ^
    ../ccstruct/blobbox.h:236:17: note: in expansion of macro ‘TRUE’
           reduced = TRUE;
                     ^~~~
Signed-off-by: NStefan Weil <sw@weilnetz.de>

ccstruct/blobbox.h

@@ -233,7 +233,7 @@ class BLOBNBOX:public ELIST_LINK
     }
     void set_reduced_box(TBOX new_box) {
       red_box = new_box;
-      reduced = TRUE;
+      reduced = true;
     }
     inT32 enclosed_area() const {
       return area;
@@ -503,8 +503,8 @@ class BLOBNBOX:public ELIST_LINK
   TBOX box;                     // bounding box
   TBOX red_box;                 // bounding box
   int area:30;                  // enclosed area
-  int joined:1;                 // joined to prev
-  int reduced:1;                // reduced box set
+  unsigned joined:1;            // joined to prev
+  unsigned reduced:1;           // reduced box set
   int repeated_set_;            // id of the set of repeated blobs
   TabType left_tab_type_;       // Indicates tab-stop assessment
   TabType right_tab_type_;      // Indicates tab-stop assessment