Add option to disable LASH, clean up configure.ac.
Add option to disable LASH, clean up configure.ac.

* Removed checks that aren't likely be needed in recent versions of gcc.
* Refactored more optional features into found-enabled pattern
* Upped the required autoconf version to 2.63 (for LT_INIT)

adiknoth/calf,adiknoth/calf,jnetterf/calf,jnetterf/calf,jnetterf/calf,adiknoth/calf,zamaudio/calf-LR4,jnetterf/calf,adiknoth/calf,zamaudio/calf-LR4,zamaudio/calf-LR4,zamaudio/calf-LR4,jnetterf/calf,zamaudio/calf-LR4,adiknoth/calf