Cosmetic: Fix a number of typos, no functional changes.

Fix various misspellings of things like "environment", "kernel",
"default" and "volatile", and throw in a couple grammar fixes.

Signed-off-by: Robert P. J. Day <rpjday@crashcourse.ca>
diff --git a/lib/hashtable.c b/lib/hashtable.c
index 644330a..c5a2b08 100644
--- a/lib/hashtable.c
+++ b/lib/hashtable.c
@@ -817,7 +817,7 @@
 	 * size of 8 per entry (= safety factor of ~5) should provide enough
 	 * safety margin for any existing environment definitions and still
 	 * allow for more than enough dynamic additions. Note that the
-	 * "size" argument is supposed to give the maximum enviroment size
+	 * "size" argument is supposed to give the maximum environment size
 	 * (CONFIG_ENV_SIZE).  This heuristics will result in
 	 * unreasonably large numbers (and thus memory footprint) for
 	 * big flash environments (>8,000 entries for 64 KB