Fixed yaml-cpp.pc file (with prefix)

yaml-cpp.pc.cmake

 prefix=@CMAKE_INSTALL_PREFIX@
 exec_prefix=@CMAKE_INSTALL_PREFIX@
-libdir=@LIB_INSTALL_DIR@
-includedir=@INCLUDE_INSTALL_DIR@
+libdir=${prefix}/@LIB_INSTALL_DIR@
+includedir=${prefix}/@INCLUDE_INSTALL_DIR@
 
 Name: Yaml-cpp
 Description: A YAML parser and emitter for C++