thunderbird: Update version from 45.7.1 to 45.8.0

Release notes [1]:

> Version 45.8.0, first offered to Release channel users on March 7,
> 2017
>
> ### What’s New ###
>
> Various security fixes [2][3]

[1] https://www.mozilla.org/en-US/thunderbird/45.8.0/releasenotes/
[2] https://www.mozilla.org/en-US/security/known-vulnerabilities/thunderbird/#thunderbird45.8
[3] https://www.mozilla.org/en-US/security/advisories/mfsa2017-07/

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-45.7.1-0
+# BEE_VERSION thunderbird-45.8.0-0
 
 SRCURL[0]="https://ftp.mozilla.org/pub/thunderbird/releases/${PKGVERSION}/source/thunderbird-${PKGVERSION}.source.tar.xz"