thumbv7[arm] support

[Karl Berry]

We received this report on automake from Kolanich (thanks):
(https://debbugs.gnu.org/cgi/bugreport.cgi?bug=43945):

    Hello. When I crosscompiled some app I had to patch some file
    generated by autoreconf -i, where I have to add thumbv7[arm] (using
    the analogy to armv7[arm] already present there) there. 

He later followed up with the necessary change, which
turned out to be for config.sub:

--- a/config.sub
+++ b/config.sub
..
-       | arm | arm[bl]e | arme[lb] | armv[2-8] | armv[3-8][lb] | armv7[arm] \
+       | arm | arm[bl]e | arme[lb] | armv[2-8] | armv[3-8][lb] | armv7[arm] | 
thumbv7[arm] \

Dmitry, or anyone, wdyt? I know little about the myriad arm
architectures. --thanks, karl.