fixed doxygen.cfg, excluded directory /tests/ from doxygen path's

Signed-off-by: Ilia Maslakov <il.smind@gmail.com>

doc/doxygen.cfg

@@ -91,7 +91,7 @@ FILE_PATTERNS          = *.c \
 RECURSIVE              = YES
 EXCLUDE                =
 EXCLUDE_SYMLINKS       = NO
-EXCLUDE_PATTERNS       = */intl/*
+EXCLUDE_PATTERNS       = */intl/* */tests/* */.git/*
 EXCLUDE_SYMBOLS        =
 EXAMPLE_PATH           = $(SRCDIR)
 EXAMPLE_PATTERNS       =