Merge pull request #3134 from AndrzejKurek/doxygen-include-fix

Add an include path to the doxyfile to fix preprocessing for docs
diff --git a/doxygen/mbedtls.doxyfile b/doxygen/mbedtls.doxyfile
index 4732271..148fa27 100644
--- a/doxygen/mbedtls.doxyfile
+++ b/doxygen/mbedtls.doxyfile
@@ -1594,7 +1594,7 @@
 # contain include files that are not input files but should be processed by
 # the preprocessor.
 
-INCLUDE_PATH           =
+INCLUDE_PATH           = ../include
 
 # You can use the INCLUDE_FILE_PATTERNS tag to specify one or more wildcard
 # patterns (like *.h and *.hpp) to filter out the header-files in the