thunderbird: Update version from 45.5.0 to 45.5.1

Release notes [1]:

> Version 45.5.1, first offered to Release channel users on November 30,
> 2016
>
> ## What’s New ##
>
> *   Fixed: Various security fixes

[1] https://www.mozilla.org/en-US/thunderbird/45.5.1/releasenotes/

thunderbird.be0

@@ -2,7 +2,7 @@
 
 #export BEE_TMP_TMPDIR=/dev/shm BEE_TMP_BUILDROOT=/dev/shm/bee-root BEE_MAKEFLAGS='-j80'
 
-# BEE_VERSION thunderbird-45.5.0-0
+# BEE_VERSION thunderbird-45.5.1-0
 
 SRCURL[0]="https://ftp.mozilla.org/pub/thunderbird/releases/${PKGVERSION}/source/thunderbird-${PKGVERSION}.source.tar.xz"