thunderbird: Update version from 45.7.0 to 45.7.1

Release notes [1]:

> Version 45.7.1, first offered to Release channel users on February 7,
> 2017
>
> ### Fixed ###
>
> *   Crash when viewing certain IMAP messages (introduced in 45.7.0)
>
> ### Known Issues ###
>
> *   Message preview pane non-functional after IMAP folder was renamed or
>     moved

[1] https://www.mozilla.org/en-US/thunderbird/45.7.1/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-45.7.0-0
+# BEE_VERSION thunderbird-45.7.1-0
 
 SRCURL[0]="https://ftp.mozilla.org/pub/thunderbird/releases/${PKGVERSION}/source/thunderbird-${PKGVERSION}.source.tar.xz"