[LinuxCNC/linuxcnc Issue#475] `configure.ac` missing checks for `inttool-extract`, `yapps` executables

Commit 8c375852 added a target that runs intltool-extract to the Makefiles, and the intltool package was added to Debian packaging in d20f8eb1, but a similar check for the executable in configure.ac is missing.

Commit fc6eb7f2 removed a bundled version of yapps and added the build dep to the Debian packaging, but similarly didn’t add it to configure.ac.

I know this is true for master, but haven’t checked 2.7.