[devel] Fixed some spelling and indentation.

pngvalid.c

diff --git a/pngvalid.c b/pngvalid.c
index 43358cb..a3a13b9 100644
--- a/pngvalid.c
+++ b/pngvalid.c
@@ -1876,7 +1876,7 @@
     * used by the library - otherwise we will get spurious errors from the
     * internal sbit style approximation.
     *
-    * The threshold test is here because otherwise the 16 to 8 convertion will
+    * The threshold test is here because otherwise the 16 to 8 conversion will
     * proceed *without* gamma correction, and the tests above will fail (but not
     * by much) - this could be fixed, it only appears with the -g option.
     */