Allow 0 to be a valid value pruning interval in C LTO API. Value 0 will cause garbage collector to run. This matches the behavior in C++ LTO API.

llvm-svn: 325303
diff --git a/llvm/include/llvm-c/lto.h b/llvm/include/llvm-c/lto.h
index 8ea2424..4eee5f1 100644
--- a/llvm/include/llvm-c/lto.h
+++ b/llvm/include/llvm-c/lto.h
@@ -784,7 +784,7 @@
 /**
  * Sets the cache pruning interval (in seconds). A negative value disables the
  * pruning. An unspecified default value will be applied, and a value of 0 will
- * be ignored.
+ * force prunning to occur.
  *
  * \since LTO_API_VERSION=18
  */