all: fixed a handful of typos

Change-Id: Ib0683f27b44e2f107cca7a8dcc01d230cbcd5700
Reviewed-on: https://go-review.googlesource.com/23404
Reviewed-by: Alan Donovan <adonovan@google.com>
diff --git a/doc/install-source.html b/doc/install-source.html
index 9a81767..1d7df3d 100644
--- a/doc/install-source.html
+++ b/doc/install-source.html
@@ -63,19 +63,19 @@
 	<code>arm64</code> (<code>AArch64</code>)
 </dt>
 <dd>
-	Supports Linux and Darwin binaries. New in 1.5 and not as well excercised as other ports.
+	Supports Linux and Darwin binaries. New in 1.5 and not as well exercised as other ports.
 </dd>
 <dt>
 	<code>ppc64, ppc64le</code> (64-bit PowerPC big- and little-endian)
 </dt>
 <dd>
-	Supports Linux binaries. New in 1.5 and not as well excercised as other ports.
+	Supports Linux binaries. New in 1.5 and not as well exercised as other ports.
 </dd>
 <dt>
 	<code>mips64, mips64le</code> (64-bit MIPS big- and little-endian)
 </dt>
 <dd>
-	Supports Linux binaries. New in 1.6 and not as well excercised as other ports.
+	Supports Linux binaries. New in 1.6 and not as well exercised as other ports.
 </dd>
 </dl>