scope private/public headers when embedding into other projects

thanks to Cameron Palmer

ssl/CMakeLists.txt

@@ -1,9 +1,3 @@
-include_directories(
-	.
-	../include
-	../include/compat
-)
-
 set(
 	SSL_SRC
 	bio_ssl.c
@@ -48,6 +42,13 @@ set(
 )
 
 add_library(ssl ${SSL_SRC})
+target_include_directories(ssl
+	PRIVATE
+		.
+	PUBLIC
+		../include
+		../include/compat)
+
 if (BUILD_SHARED_LIBS)
 	export_symbol(ssl ${CMAKE_CURRENT_SOURCE_DIR}/ssl.sym)
 	target_link_libraries(ssl crypto)