In BCS, allow fractional part of fixed-point literal to have no digits

ACS allows this. For compatibility reasons, allow it in BCS.

doc/grammar.txt

@@ -808,7 +808,7 @@ hexadecimal-number:
    0[xX][0-9a-fA-F]+([']?[0-9a-fA-F]+)*
 
 fixed-point-number:
-   [0-9]+([']?[0-9]+)*[.][0-9]+([']?[0-9]+)*
+   [0-9]+([']?[0-9]+)*[.]([0-9]+([']?[0-9]+)*)?
 
 radix-number:
    [0-9]+([']?[0-9]+)*[_rR][0-9a-zA-Z]+([']?[0-9a-zA-Z]+)*

doc/grammar_acs.txt

@@ -432,7 +432,7 @@ hexadecimal-number:
    0[xX][0-9a-fA-F]*
 
 fixed-point-number:
-   [0-9]+[.][0-9]+
+   [0-9]+[.][0-9]*
 
 radix-number:
    [0-9]+[_][0-9a-zA-Z]+

doc/grammar_acs95.txt

@@ -263,7 +263,7 @@ hexadecimal-number:
    0[xX][0-9a-fA-F]*
 
 fixed-point-number:
-   [0-9]+[.][0-9]+
+   [0-9]+[.][0-9]*
 
 radix-number:
    [0-9]+[_][0-9a-zA-Z]+

src/parse/token/source.c

@@ -2358,14 +2358,13 @@ void read_token( struct parse* parse, struct token* token ) {
             "invalid digit in fractional part of fixed-point literal" );
          p_bail( parse );
       }
-      else if ( text->value[ text->length - 1 ] == '.' ) {
-         struct pos pos = { parse->source->line, column,
-            parse->source->file_entry_id };
-         p_diag( parse, DIAG_POS_ERR, &pos,
-            "no digits found in fractional part of fixed-point literal" );
-         p_bail( parse );
-      }
       else {
+         if ( text->value[ text->length - 1 ] == '.' ) {
+            struct pos pos = { parse->source->line, column,
+               parse->source->file_entry_id };
+            p_diag( parse, DIAG_POS | DIAG_WARN, &pos,
+               "no digits found in fractional part of fixed-point literal" );
+         }
          tk = TK_LIT_FIXED;
          goto state_finish;
       }