README: Mention optional nettle dependency.

One of the USB load drivers depends on the nettle library. Add it to the
README file as another optional dependency.

diff --git a/README b/README
index 768c8ca2b6612d1850d69f8f25e95c830850aef7..ecdc2fd92875f35f14dd23c629c8a46503a289e7 100644 (file)
--- a/README
+++ b/README
@@ -49,6 +49,7 @@ Requirements for the C library:
  - libgpib (optional, used by some drivers)
  - libieee1284 (optional, used by some drivers)
  - libgio >= 2.32.0 (optional, used by some drivers)
+ - nettle (optional, used by some drivers)
  - check >= 0.9.4 (optional, only needed to run unit tests)
  - doxygen (optional, only needed for the C API docs)
  - graphviz (optional, only needed for the C API docs)