cmake: move modules into the "cmake/" top level dir

Our custom CMake module currently live in "cmake/Modules". As the
"cmake/" directory doesn't contain anything except the "Modules"
directory, it doesn't really make sense to have the additional
intermediate directory. So let's instead move the modules one level up
into the "cmake/" top level directory.

CMakeLists.txt

@@ -25,7 +25,7 @@ IF(POLICY CMP0054)
 ENDIF()
 
 # Add find modules to the path
-SET(CMAKE_MODULE_PATH ${CMAKE_MODULE_PATH} "${libgit2_SOURCE_DIR}/cmake/Modules/")
+set(CMAKE_MODULE_PATH ${CMAKE_MODULE_PATH} "${libgit2_SOURCE_DIR}/cmake/")
 
 INCLUDE(CheckLibraryExists)
 INCLUDE(CheckFunctionExists)