fixed wrong case (just a cosmetic change)

cmake/Modules/Findreadline.cmake

@@ -3,11 +3,11 @@ find_path( readline_ROOT_DIR NAMES include/readline/readline.h )
 
 # Search for include directory
 find_path( readline_INCLUDE_DIR NAMES readline/readline.h
-                                HINTS ${Readline_ROOT_DIR}/include )
+                                HINTS ${readline_ROOT_DIR}/include )
 
 # Search for library
 find_library( readline_LIBRARY NAMES readline
-                               HINTS ${Readline_ROOT_DIR}/lib )
+                               HINTS ${readline_ROOT_DIR}/lib )
 
 # use a macro provided by CMake to check if all the listed arguments are valid and set readline_FOUND accordingly
 include(FindPackageHandleStandardArgs)