Perform transitivity chaining for non-strict real number inequality.
When applied to a theorem A |- s <= t where s and t have type real, the
rule REAL_LE_IMP returns A |- !x1...xn z. t <= z ==> s <= z, where z is
some variable and the x1,...,xn are free variables in s and t.
Fails if applied to a theorem whose conclusion is not of the form `s <= t`
for some real number terms s and t.
# REAL_LE_IMP (REAL_ARITH `x:real <= abs(x)`);;
val it : thm = |- !x z. abs x <= z ==> x <= z
Can make transitivity chaining in goals easier, e.g. by
FIRST_ASSUM(MATCH_MP_TAC o REAL_LE_IMP).