Significant rewrite of the code used to invoke the C compiler. The most

Significant rewrite of the code used to invoke the C compiler.  The most
important functional change is that the source is no longer piped to the
compiler; instead, the source file name (which now ends in .c) is passed
on the command line.  This makes it *much* easier to support non-GNU
compilers.

The cc_command parameter processed by a custom function instead of sprintf;
"%s" is replaced with the source file name, "%o" is replaced with the output
file name, and "%%" is replaced with a single "%".

git-svn-id: svn+ssh://projects.linpro.no/svn/varnish/trunk@2249 d4fa192b-c00b-0410-8231-f00ffab90ce4