[apr-api-docs] Add GENERATE_HTML=YES, because doxygen 1.8.7 does not seem to be doing that by default.

[bojan]

commit 2e3f013b7203c7811857ea1ae7305de04480e9de
Author: Bojan Smojver <bojan at rexursive.com>
Date:   Tue Jun 10 09:40:06 2014 +1000

    Add GENERATE_HTML=YES, because doxygen 1.8.7 does not seem to be doing that
    by default.

 doxygen.conf |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)
---
diff --git a/doxygen.conf b/doxygen.conf
index 29c2cbf..e8f6167 100644
--- a/doxygen.conf
+++ b/doxygen.conf
@@ -36,3 +36,4 @@ EXCLUDE_PATTERNS="*/acconfig.h" \
 
 GENERATE_TAGFILE=docs/dox/apr.tag
 
+GENERATE_HTML=YES