Fix CMake CMP0167 Warning

When I was building the source code of msgpack-c, I encountered a
CMP0167 warning. Although it did not affect the code building process,
it was a minor flaw. I believed that adding CONFIG to
`find_package(Boost REQUIRED)` could solve the issue. Therefore, I
organized the code repository and fixed this minor issue.

Author: SSDGADsss

CMakeLists.txt

@@ -79,7 +79,7 @@ IF (MSGPACK_USE_BOOST)
         SET (Boost_USE_STATIC_LIBS FALSE)
     ENDIF ()
 
-    FIND_PACKAGE (Boost REQUIRED)
+    FIND_PACKAGE (Boost REQUIRED CONFIG)
 ELSE ()
     TARGET_COMPILE_DEFINITIONS(msgpack-cxx INTERFACE MSGPACK_NO_BOOST)
 ENDIF ()

example/boost/CMakeLists.txt

@@ -1,4 +1,4 @@
-FIND_PACKAGE (Boost REQUIRED)
+FIND_PACKAGE (Boost REQUIRED CONFIG)
 FIND_PACKAGE (Threads REQUIRED)
 FIND_PACKAGE (ZLIB REQUIRED)
 

example/cpp03/CMakeLists.txt

@@ -1,6 +1,6 @@
 FIND_PACKAGE (Threads REQUIRED)
 
-FIND_PACKAGE (Boost COMPONENTS timer)
+FIND_PACKAGE (Boost COMPONENTS timer CONFIG)
 
 LIST (APPEND exec_PROGRAMS
     class_intrusive.cpp

example/x3/CMakeLists.txt

@@ -1,5 +1,5 @@
 IF (MSGPACK_USE_X3_PARSE AND MSGPACK_DEFAULT_API_VERSION VERSION_GREATER 1)
-    FIND_PACKAGE (Boost REQUIRED COMPONENTS context)
+    FIND_PACKAGE (Boost REQUIRED COMPONENTS context CONFIG)
     FIND_PACKAGE (Threads REQUIRED)
 
     LIST (APPEND exec_PROGRAMS

fuzz/CMakeLists.txt

@@ -1,5 +1,5 @@
 FIND_PACKAGE (Threads REQUIRED)
-FIND_PACKAGE (Boost REQUIRED COMPONENTS filesystem unit_test_framework)
+FIND_PACKAGE (Boost REQUIRED COMPONENTS filesystem unit_test_framework CONFIG)
 
 LIST (APPEND check_PROGRAMS
     regression_runner.cpp

test/CMakeLists.txt

@@ -1,6 +1,6 @@
 FIND_PACKAGE (Threads REQUIRED)
 FIND_PACKAGE (ZLIB)
-FIND_PACKAGE (Boost REQUIRED COMPONENTS unit_test_framework)
+FIND_PACKAGE (Boost REQUIRED COMPONENTS unit_test_framework CONFIG)
 
 LIST (APPEND check_PROGRAMS
     array_ref.cpp