Fix occurrences of Wextra-semi-stmt

Bug: http://b/123023349

Upcoming clang update adds a new diagnostic about empty statements from
extraneous semicolons.  Remove the semicolon at the end of DNG_ASSERT
since most uses of the macro treat it as a function call and add a
semicolon after the macro statement.  Fix the one use of DNG_ASSERT that
wasn't using a macro.

Test: Build with new clang.
Change-Id: I7c53fe4d19441446e2c5b7871b4bf07dfffd154c
diff --git a/source/dng_assertions.h b/source/dng_assertions.h
index dc998fa..0377350 100644
--- a/source/dng_assertions.h
+++ b/source/dng_assertions.h
@@ -59,7 +59,7 @@
 /// \param x Predicate which must be true.
 /// \param y String to display if x is not true.
-#define DNG_ASSERT(x,y)
+#define DNG_ASSERT(x,y) do { } while(false)
diff --git a/source/dng_mosaic_info.cpp b/source/dng_mosaic_info.cpp
index 0a51d9b..dde2e31 100644
--- a/source/dng_mosaic_info.cpp
+++ b/source/dng_mosaic_info.cpp
@@ -104,7 +104,7 @@
 	// Add element to list.
-	DNG_ASSERT (fCount < kMaxCount, "Too many kernel entries")
+	DNG_ASSERT (fCount < kMaxCount, "Too many kernel entries");
 	fDelta    [fCount] = delta;
 	fWeight32 [fCount] = weight;