Support building Asterisk for Raspberry Pi/Raspbian with hard-float support

Building Asterisk on Raspbian with hard-float support fails as it uses the
string 'linux-gnueabihf' for host os, as opposed to 'linux-gnueabi'. This patch
modifies the configure script for Asterisk such that it will match on any
string beginning with 'linux-gnueabi', as opposed to requiring an explicit
match.

(closes issue ASTERISK-21006)
Reported by: Christian Hesse
Tested by: Christian Hesse
patches:
  linux-gnueabihf.patch uploaded by Christian Hesse (license 6459)
  linux-gnueabihf-autoconf.patch uploaded by Christian Hesse (license 6459)
........

Merged revisions 380520 from http://svn.asterisk.org/svn/asterisk/branches/1.8


git-svn-id: http://svn.asterisk.org/svn/asterisk/branches/11@380521 f38db490-d61c-443f-a65b-d21fe96a405b