genltl: add --spec-patterns as an alias to --dac-patterns

* bin/genltl.cc: Here.
* NEWS: Mention it.

NEWS

@@ -5,6 +5,8 @@ New in spot 2.3.2.dev (not yet released)
   - ltldo and ltlcross learned shorthands to talk to ltl2da, ltl2dpa,
     and ltl2ldba (from Owl) without needing to specify %f>%O.
 
+  - genltl learned --spec-patterns as an alias for --dac-patterns
+
   Bug fixes:
 
   - In "lenient" mode the parser would fail to recover from

bin/genltl.cc

@@ -264,6 +264,7 @@ static const argp_option options[] =
     { "dac-patterns", OPT_DAC_PATTERNS, "RANGE", OPTION_ARG_OPTIONAL,
       "Dwyer et al. [FMSP'98] Spec. Patterns for LTL "
       "(range should be included in 1..55)", 0 },
+    OPT_ALIAS(spec-patterns),
     { "eh-patterns", OPT_EH_PATTERNS, "RANGE", OPTION_ARG_OPTIONAL,
       "Etessami and Holzmann [Concur'00] patterns "
       "(range should be included in 1..12)", 0 },