koptocr: fix build with GCC 15 (#61)

koptocr: fix and optimize `bitmap2pix` implementation (#60)

koptocr: fix `k2pdfopt_tocr_end` prototype (#59)

koptocr: cleanup prototypes / exports (#58)

fix uninitialized memory access (#57)

improve OCR API (#56)

support building a static library (#55)

cleanup unnecessary exports (#53)

add color support (#54)

fix possible segfault when defining `WILLUSDEBUGX` (#52)

only export the symbols needed for koreader (#51)

trim the fat (#50)

fix `k2printf` prototype

use `k2printf` for debug traces

update to k2pdfopt 2.55