Add support for --enable-builtins to configure

--enable-builtins will allow users to include some extensions in the
WiredTiger library by default. This saves needing to load libraries
at runtime.
More implementation of --with-builtins=

Not yet linking in the library properly.
Link builtin extensions directly into libwiredtiger.la.
Fix zlib builtin build, simplify parsing the list of builtins, don't list "./Makefile" as a generated file.
More --with-builtins implementation.

Backout change to how builtins list is parsed, I was seeing:
../configure: line 5439: printf %s\n: command not found
Fix quoting in m4 script.
Update the API exposed by extensions that can be builtin.

Otherwise multiple builtin extensions will conflict on
the wiredtiger_extension_init function.
Merge branch 'develop' into builtin-extensions
Merge pull request #1081 from wiredtiger/builtin-extensions

Add support for "builtin extensions" that don't require dynamically loading a shared object.