Add end-to-end SMT FPA test for FMA special cases

Run main_03.c (NaN, infinity, 0*inf) through an external SMT solver
with --smt2 --fpa to verify the fp.fma emission produces correct
verification results, not just correct syntax.

Co-authored-by: Kiro <kiro-agent@users.noreply.github.com>

Author: tautschnig

regression/cbmc-library/fma/test_fpa_special_cases.desc

@@ -0,0 +1,11 @@
+CORE smt-backend
+special_cases.c
+--smt2 --fpa --no-built-in-assertions
+^EXIT=0$
+^SIGNAL=0$
+^VERIFICATION SUCCESSFUL$
+--
+^warning: ignoring
+--
+Run FMA special cases through an external SMT solver with FPA theory.
+Verifies NaN, infinity, and 0*inf handling end-to-end.