Fix reglap for procedures that use both sizes of reg_float.

Fix reglap for procedures that use both sizes of reg_float.

After the RA phase of ego, a procedure may put single-word and
double-word values in the same reg_float.  Then ncg will use both
LOCAL and DLOCAL tokens at the same offset.

I add isregvar_size() to ncg.  It receives the size of the LOCAL or
DLOCAL token, and picks the register of the correct size.  This fixes
a problem where ncg got the wrong-size register and corrupted the
stack.  This problem caused one of my test programs to segfault from
stack underflow.

Also adjust how fixregvars() handles both sizes.