c-API: move implementation and header files into core/src

This helps in building the C_API for the rust wrapper in a sub-directory.

Also remove the outdated inclusion of ../zxing.cmake

core/CMakeLists.txt

@@ -3,7 +3,6 @@ cmake_minimum_required(VERSION 3.15)
 project (ZXing VERSION "2.2.1")
 set (ZXING_SONAME 3) # see https://github.com/zxing-cpp/zxing-cpp/issues/333
 
-include(../zxing.cmake)
 if (BUILD_SHARED_LIBS)
     set(CMAKE_POSITION_INDEPENDENT_CODE ON)
 endif()
@@ -138,8 +137,8 @@ if (BUILD_READERS)
         src/ThresholdBinarizer.h
         src/WhiteRectDetector.h
         src/WhiteRectDetector.cpp
-        $<$<BOOL:${BUILD_C_API}>:${CMAKE_SOURCE_DIR}/wrappers/c/zxing-c.h>
-        $<$<BOOL:${BUILD_C_API}>:${CMAKE_SOURCE_DIR}/wrappers/c/zxing-c.cpp>
+        $<$<BOOL:${BUILD_C_API}>:src/zxing-c.h>
+        $<$<BOOL:${BUILD_C_API}>:src/zxing-c.cpp>
     )
 endif()
 if (BUILD_WRITERS)
@@ -178,7 +177,7 @@ if (BUILD_READERS)
         src/ReaderOptions.h
         src/Result.h
         src/StructuredAppend.h
-        $<$<BOOL:${BUILD_C_API}>:${CMAKE_SOURCE_DIR}/wrappers/c/zxing-c.h>
+        $<$<BOOL:${BUILD_C_API}>:${CMAKE_CURRENT_SOURCE_DIR}/src/zxing-c.h>
     )
 endif()
 if (BUILD_WRITERS)