[enhancement] update openmp version & doxygen path fix (TheAlgorithms…

…#1021)

* exclude 'build' directory from doxygen

* bump openmp version to 3.0

OpenMP >= v3.0 supports signed and unsigned for loop variables

CMakeLists.txt

@@ -18,7 +18,7 @@ endif(MSVC)
 
 option(USE_OPENMP "flag to use OpenMP for multithreading" ON)
 if(USE_OPENMP)
-    find_package(OpenMP)
+    find_package(OpenMP 3.0 COMPONENTS CXX)
     if (OpenMP_CXX_FOUND)
         message(STATUS "Building with OpenMP Multithreading.")
     else()
@@ -57,6 +57,7 @@ if(DOXYGEN_FOUND)
     set(DOXYGEN_STRIP_CODE_COMMENTS NO)
     set(DOXYGEN_EXT_LINKS_IN_WINDOW YES)
     set(DOXYGEN_BUILTIN_STL_SUPPORT YES)
+    set(DOXYGEN_EXCLUDE_PATTERNS */build/*)
     set(DOXYGEN_ENABLE_PREPROCESSING YES)
     set(DOXYGEN_CLANG_ASSISTED_PARSING YES)
     set(DOXYGEN_FILE_PATTERNS *.cpp *.h *.hpp *.md)