Linux: Add general autoconf macro for Linux kernel
Add AC_CHECK_LINUX_BUILD() to do a standardised Linux build, which
takes a "checking" message, the autoconf variable to use to cache
the results, headers and code to run, preprocessor variable to
define, and a description of that variable.
Reimplement all of our existing check macros in terms of this one,
resolving many typos along the way.
Change-Id: I41988c83fcdbfbf8152f6dd0e7c4bd16c7a04240
Reviewed-on: http://gerrit.openafs.org/1854
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Tested-by: Derrick Brashear <shadow@dementia.org>