configure.ac: Remove obsolete macros
configure.ac: Remove obsolete macros

The newer macros that replace the obsolete ones are already present in configure.ac.

  * AC_PROG_LIBTOOL -> LT_INIT
  * AC_LANG_CPLUSPLUS -> AC_LANG([C++])
UB-Mannheim/tesseract,stweil/tesseract,UB-Mannheim/tesseract,jbarlow83/tesseract,amitdo/tesseract,UB-Mannheim/tesseract,stweil/tesseract,amitdo/tesseract,UB-Mannheim/tesseract,UB-Mannheim/tesseract,jbarlow83/tesseract,amitdo/tesseract,amitdo/tesseract,amitdo/tesseract,tesseract-ocr/tesseract,stweil/tesseract,jbarlow83/tesseract,stweil/tesseract,jbarlow83/tesseract,tesseract-ocr/tesseract,tesseract-ocr/tesseract,tesseract-ocr/tesseract,tesseract-ocr/tesseract,jbarlow83/tesseract,stweil/tesseract