K 10
svn:author
V 6
grehan
K 8
svn:date
V 27
2015-02-18T19:27:51.775968Z
K 7
svn:log
V 290
Restore the ability to use clang as an external compiler. This was
inadvertently removed when support for external GCC was added.

Deprecate XFLAGS in favour of the newer XCFLAGS/XCXXFLAGS.

Tested with:	make universe, make CROSS_COMPILER_PREFIX=/usr/bin/ buildworld
Reviewed by:	imp, bapt

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