* doc/bison.texinfo: Update.

* doc/bison.1 (mandoc): Update.
* src/system.h (EXT_GUARD_C, EXT_STYPE_H): Remove .c and .h.
* src/files.c: Support output files extensions computing.
(src_extension): New static variable.
(header_extension): New static variable.
(tr): New function.
(get_extension_index): New function, gets the index of an extension
filename in a string.
(compute_exts_from_gf): New function, computes extensions from the
grammar file extension.
(compute_exts_from_src): New functions, computes extensions from the
C source file extension, file given by ``-o'' option.
(compute_base_names): Update.
(output_files): Update.

doc/bison.1

@@ -71,13 +71,22 @@ Unlike
 .IR yacc ,
 the generated files do not have fixed names, but instead use the prefix
 of the input file.
+Moreover, if you need to put 
+.IR C++
+code in the input file, you can end his name by a C++-like extension
+(.ypp or .y++), then bison will follow your extension to name the 
+output file (.cpp or .c++).
 For instance, a grammar description file named
-.B parse.y
+.B parse.yxx
 would produce the generated parser in a file named
-.BR parse.tab.c ,
+.BR parse.tab.cxx ,
 instead of
 .IR yacc 's
-.BR y.tab.c .
+.BR y.tab.c 
+or old 
+.IR Bison
+versions
+.BR parse.tab.c .
 .PP
 This description of the options that can be given to
 .I bison