CLEANUP: buffer: replace b_drop() with b_free()
Since last commit there's no point anymore in having two variants of the
same function, let's switch to b_free() only. __b_drop() was renamed to
__b_free() for obvious consistency reasons.
diff --git a/doc/internals/buffer-api.txt b/doc/internals/buffer-api.txt
index abb5e9f..6d192c1 100644
--- a/doc/internals/buffer-api.txt
+++ b/doc/internals/buffer-api.txt
@@ -567,10 +567,7 @@
| | never calls malloc(), so it can fail
| | even if some memory is available
--------------------+------------------+---------------------------------------
-__b_drop | buffer *buf | releases <buf> which must be allocated
- | ret: void | and marks it empty
---------------------+------------------+---------------------------------------
-b_drop | buffer *buf | releases <buf> only if it is allocated
+__b_free | buffer *buf | releases <buf> which must be allocated
| ret: void | and marks it empty
--------------------+------------------+---------------------------------------
b_free | buffer *buf | releases <buf> only if it is allocated