* tests/gpgscm/scheme.c (S_FLAG_TAIL_CONTEXT): New macro. This flag
indicates that the interpreter is evaluating an expression in a tail
context (see R5RS, section 3.5).
(opexe_0): Clear and set the flag according to the rules layed out in
R5RS, section 3.5.
(opexe_1): Likewise.
Signed-off-by: Justus Winter <justus@g10code.com>