GC-safety bug

[Bruno H. <br...@cl...>]

Found by g++ 3.4.0 when running ansi-tests:
In comptran.d:618 (function N_cosh_N) the variable erg, when passed as
first argument to F_R_float_F, is stale. Sam, can you please look at it,
while I continue on the weak pointers?

Bruno