firefox: Update version from 51.0 to 51.0.1

Release notes [1]:

> Version 51.0.1, first offered to Release channel users on January 26,
> 2017
>
> ### Fixed ###
>
> *   Reference link to 51.0 release notes
> *   Geolocation not working on Windows (Bug 1333516)
> *   Multiprocess incompatibility did not correctly register with some
>     add-ons (Bug 1333423)

[1] https://www.mozilla.org/en-US/firefox/51.0.1/releasenotes/

firefox.be0

@@ -2,7 +2,7 @@
 
 #export BEE_TMP_TMPDIR=/dev/shm BEE_TMP_BUILDROOT=/dev/shm/bee-root BEE_MAKEFLAGS='-j80'
 
-# BEE_VERSION firefox-51.0-0
+# BEE_VERSION firefox-51.0.1-0
 
 SRCURL[0]="https://ftp.mozilla.org/pub/firefox/releases/${PKGVERSION}/source/firefox-${PKGVERSION}.source.tar.xz"