adds the C99 _Bool type (#39)

Note, this type is different from any integer types as, in
```
_Bool a=1, b=2;
assert(a == b);
```
the assertion holds.

Author: ivg

frontc/cabs.ml

@@ -36,6 +36,7 @@ and storage =
 and base_type =
   | NO_TYPE    (** Old K&R declaration without type *)
   | VOID     (** "void" type *)
+  | BOOL     (** C99 boolean (_Bool) type  *)
   | CHAR of sign   (** "char" type with sign modifier *)
   | INT of size * sign (** "int" type with size and sign modifiers *)
   | BITFIELD of sign * expression

frontc/clexer.mll

@@ -153,6 +153,7 @@ let keywords =
     ("__restrict", id RESTRICT);
     ("restrict", id RESTRICT);
     ("char", id CHAR);
+    ("_Bool", id BOOL);
     ("int", id INT);
     ("float", id FLOAT);
     ("double", id DOUBLE);

frontc/cparser.mly

@@ -731,6 +731,7 @@ only_dec:
 /*** Base type ***/
 qual_type:
   |  VOID       {(VOID, [])}
+  |  BOOL       {(BOOL, [])}
   |  CHAR       {(CHAR NO_SIGN, [])}
   |  INT        {(INT (NO_SIZE, NO_SIGN), [])}
   |  FLOAT      {(FLOAT false, [])}

frontc/cprint.ml

@@ -158,6 +158,7 @@ let rec print_base_type typ =
   match typ with
     NO_TYPE -> ()
   | VOID -> print "void"
+  | BOOL -> print "_Bool"
   | CHAR sign -> print ((get_sign sign) ^ "char")
   | INT (size, sign) -> print ((get_sign sign) ^ (get_size size) ^ "int")
   | BITFIELD (sign, _) -> print ((get_sign sign) ^ "int")

frontc/ctokens.mly

@@ -7,7 +7,7 @@
 %token <Cabs.gnu_attrs> GNU_ATTRS
 
 %token EOF
-%token CHAR INT DOUBLE FLOAT VOID
+%token CHAR BOOL INT DOUBLE FLOAT VOID
 %token ENUM STRUCT TYPEDEF UNION
 %token SIGNED UNSIGNED LONG SHORT COMPLEX
 %token VOLATILE EXTERN STATIC CONST AUTO REGISTER RESTRICT

frontc/ctoxml.ml

@@ -235,6 +235,7 @@ and convert_type _type =
   let base_type name = Cxml.new_elt name [] [] in
   match _type with
     NO_TYPE -> convert_type (INT (NO_SIZE, NO_SIGN))
+  | BOOL -> base_type "bool"
   | VOID -> base_type "void"
   | CHAR NO_SIGN
   | CHAR SIGNED -> base_type "char"