cmake: add include headers to libnfs

This change adds the main include dir to the include directories for
cmake such that when integrating libnfs with another project, this dir
is added to the include list.

lib/CMakeLists.txt

@@ -9,6 +9,7 @@ set(SOURCES init.c
 
 add_library(nfs ${SOURCES})
 target_link_libraries(nfs PUBLIC ${core_DEPENDS})
+target_include_directories(nfs PUBLIC ../include)
 set_target_properties(nfs PROPERTIES
                           VERSION ${PROJECT_VERSION}
                           SOVERSION ${SOVERSION})