bug#19631: Libtoolize doesn't recognise local installations of m4

[Riley Baird]

Hi,

If m4 is installed from source into the default location of
/usr/local/bin/m4, libtoolise cannot find it when run from autogen.sh.
This problem can be fixed by the command `export M4=/usr/local/bin/m4`,
but automatic recognition of this path would be best. I am running
OpenBSD 5.6.

# ./autogen.sh
creating libtransmission/version.h
libtoolize:   error: One of these is required:
libtoolize:                 gm4 gnum4 m4
libtoolize:   error: Please install GNU M4, or 'export M4=/path/to/gnu/m4'.
autoreconf: libtoolize failed with exit status: 1

Yours thankfully,

Riley Baird