Add autogen.sh to source tarball.

[randy-waterhouse]

Closes issue #4997 and restores consistency with the "To Build" instructions in doc/build-unix.md file packaged with the source tarball.

[jgarzik]

Concept ACK - though why not use EXTRA_DIST?

[randy-waterhouse]

We use the noinst because this script is packaged with the src only for building/dev but not to be installed in system directories as are execution/docs/helper script, etc files. tl;dr it gets ignored by the "make install" step but is packaged with src for building/dev.

[jgarzik]

@randy-waterhouse EXTRA_DIST files are not installed with "make install"

[randy-waterhouse]

@jgarzik oh yes right,dist_noinst_SCRIPTS preserves attributes as they are in the source, and treats it correctly as if it is a source script file with autotool rules that apply to SCRIPTS (that should not be installed) http://www.gnu.org/software/automake/manual/html_node/Scripts.html#Scripts EXTRA_DIST is for files that cannot be handled by regular dist variables and is a generic call that just dists files/directories of all types. As a design philosophy I think executable scripts should be placed clearly up front and treated as an executable script by the build system, with all that implies.

[laanwj]

utACK

[theuni]

ut ACK