Convert underscores to dashes in some %define variable names.

For now, just api.push-pull and lr.keep-unreachable-states.
Maintain old names for backward compatibility.
* NEWS (2.5): Document.
* data/c.m4 (b4_identification): Update comment.
* data/yacc.c: Update access.
* doc/bison.texinfo: Update.
* etc/bench.pl.in (bench_grammar): Update use.
* src/files.c (tr): Move to...
* src/getargs.c, src/getargs.h (tr): ... here because I can't
think of a better place to expose it.  My logic is that, for all
uses of tr so far, command-line arguments can be involved, and
getargs.h is already included.
* src/main.c (main): Update access.
* src/muscle_tab.c (muscle_percent_define_insert): Convert old
variable names to new variable names before assigning value.
* src/reader.c (reader): Update setting default.
* tests/calc.at: Update uses.
* tests/conflicts.at (Unreachable States After Conflict
Resolution): Update use.
* tests/input.at (%define enum variables): Update use.
(%define backward compatibility): New test group.
* tests/push.at: Update uses.
* tests/reduce.at: Update uses.
* tests/torture.at: Update uses.

tests/reduce.at

@@ -396,7 +396,7 @@ AT_TEST_LR_TYPE([[Single State Split]],
 [[%left 'a'
 // Conflict resolution renders state 12 unreachable for canonical LR(1).  We
 // keep it so that the paser table diff is easier to code.
-%define lr.keep_unreachable_states]],
+%define lr.keep-unreachable-states]],
 [[
 S: 'a' A 'a' /* rule 1 */
  | 'b' A 'b' /* rule 2 */
@@ -629,7 +629,7 @@ AT_TEST_LR_TYPE([[Lane Split]],
 [[%left 'a'
 // Conflict resolution renders state 16 unreachable for canonical LR(1).  We
 // keep it so that the paser table diff is easier to code.
-%define lr.keep_unreachable_states]],
+%define lr.keep-unreachable-states]],
 [[
 /* Similar to the last test case set but two states must be split.  */
 S: 'a' A 'a' /* rule 1 */
@@ -873,7 +873,7 @@ AT_TEST_LR_TYPE([[Complex Lane Split]],
 [[%left 'a'
 // Conflict resolution renders state 16 unreachable for canonical LR(1).  We
 // keep it so that the paser table diff is easier to code.
-%define lr.keep_unreachable_states]],
+%define lr.keep-unreachable-states]],
 [[
 /* Similar to the last test case set but forseeing the S/R conflict from the
    first state that must be split is becoming difficult.  Imagine if B were
@@ -1139,7 +1139,7 @@ dnl PARSER-EXIT-VALUE, PARSER-STDOUT, PARSER-STDERR
 ]])])
 
 AT_TEST_LR_TYPE([[Split During Added Lookahead Propagation]],
-[[%define lr.keep_unreachable_states]],
+[[%define lr.keep-unreachable-states]],
 [[
 /* The partial state chart diagram below is for LALR(1).  State 0 is the start
    state.  States are iterated for successor construction in numerical order.