* tests/testsuite.at (AT_CHECK): When checking if $1 starts with

* tests/testsuite.at (AT_CHECK): When checking if $1 starts with
`bison ', use m4_index instead of m4_substr since chopping up a string
containing M4-special characters causes problems here.

Fix a couple of bugs related to special characters in user-specified
file names, and make it easier for skeletons to compute output file
names with the same file name prefix as Bison-computed output file
names.
* data/glr.cc, data/push.c, data/yacc.c: In @output, use
b4_parser_file_name and b4_spec_defines_file instead of
@output_parser_name@ and @output_header_name@, which are now redundant.
* data/glr.c, data/lalr1.cc: Likewise.  Also, in header #include's, use
b4_parser_file_name, b4_spec_defines_file, and the new
@basename(FILENAME@) instead of @output_parser_name@ and
@output_header_name@, which inappropriately escaped the file names as
C string literals.
* src/files.c (all_but_ext): Remove static qualifier.
(compute_output_file_names): Move `free (all_but_ext)' to...
(output_file_names_free): ... here since all_but_ext is needed later.
* src/files.h (all_but_ext): Extern.
* src/muscle_tab.h (MUSCLE_INSERT_STRING_RAW): New macro that does
exactly what MUSCLE_INSERT_STRING used to do.
(MUSCLE_INSERT_STRING): Use MUSCLE_OBSTACK_SGROW so that M4-special
characters are escaped properly.
* src/output.c (prepare): Define muscle file_name_all_but_ext as
all_but_ext.
For pkgdatadir muscle, maintain previous functionality by using
MUSCLE_INSERT_STRING_RAW instead of MUSCLE_INSERT_STRING.  The problem
is that b4_pkgdatadir is used inside m4_include in the skeletons, so
digraphs would never be expanded.  Hopefully no one has M4-special
characters in his Bison installation path.
* src/scan-skel.l: Don't parse @output_header_name@ and
@output_parser_name@ anymore since they're now redundant.
In @output, use decode_at_digraphs.
Parse a new @basename command that invokes last_component.
(decode_at_digraphs): New.
(BASE_QPUTS): Remove unused.
* tests/output.at (AT_CHECK_OUTPUT_FILE_NAME): New macro.
(Output file name): New tests.