little bug in fft additions
added runtime/extempore.xtm

this file is loaded by all processes on startup AFTER llvmti and
llvmir. extempore.xtm is for xtlang what scheme.xtm is for scheme.
it should be used sparingly (i.e. only for MUST HAVE things)
a little setup for randomf cosd etc.
added letz also cleaned bug

this change MAY actually break things (i.e. xtlang complilation) so
let me know if you have any trouble over the coming days.. I have
tested sucessfully against xtlang_test and create-stlib, so hopefully
everything is ok.  Just a warning.
bad signature for convolution
fixed up general convolution example (time domain)
small changes
should check type also!
remove log prints for TREADMILL tests
convolution update to real fft
cleaner
metro update