Doc: Remove redundant info from documentation of -ansi.

The -ansi option has essentially been superseded by the more general
-std= option, and all the additional information about its effects is
already covered elsewhere in the manual.  I also cleaned up some
confusing text about alternate keywords that I noticed while
confirming this.

gcc/ChangeLog
	* doc/extend.texi (Alternate Keywords): Clean up text and remove
	discussion of "restrict", which is not a GNU extension at all.
	* doc/invoke.texi (C Dialect Options): Remove detailed discussion.

Author: Sandra Loosemore

gcc/doc/extend.texi

@@ -13049,17 +13049,13 @@ is taken as the minimum size, ignoring how many instructions GCC thinks it is.
 @cindex keywords, alternate
 
 @option{-ansi} and the various @option{-std} options disable certain
-keywords.  This causes trouble when you want to use GNU C extensions, or
-a general-purpose header file that should be usable by all programs,
-including ISO C programs.  The keywords @code{asm}, @code{typeof} and
+keywords that are GNU C extensions.
+Specifically, the keywords @code{asm}, @code{typeof} and
 @code{inline} are not available in programs compiled with
-@option{-ansi} or @option{-std} (although @code{inline} can be used in a
-program compiled with @option{-std=c99} or a later standard).  The
-ISO C99 keyword
-@code{restrict} is only available when @option{-std=gnu99} (which will
-eventually be the default) or @option{-std=c99} (or the equivalent
-@option{-std=iso9899:1999}), or an option for a later standard
-version, is used.
+@option{-ansi} or a @option{-std=} option specifying an ISO standard that
+doesn't define the keyword.  This causes trouble when you want to use
+these extensions in a header file that can be included in programs that may
+be compiled with with such options.
 
 The way to solve these problems is to put @samp{__} at the beginning and
 end of each problematical keyword.  For example, use @code{__asm__}

gcc/doc/invoke.texi

@@ -2386,39 +2386,6 @@ accepts:
 In C mode, this is equivalent to @option{-std=c90}. In C++ mode, it is
 equivalent to @option{-std=c++98}.
 
-This turns off certain features of GCC that are incompatible with ISO
-C90 (when compiling C code), or of standard C++ (when compiling C++ code),
-such as the @code{asm} and @code{typeof} keywords, and
-predefined macros such as @code{unix} and @code{vax} that identify the
-type of system you are using.  It also enables the undesirable and
-rarely used ISO trigraph feature.  For the C compiler,
-it disables recognition of C++ style @samp{//} comments as well as
-the @code{inline} keyword.
-
-The alternate keywords @code{__asm__}, @code{__extension__},
-@code{__inline__} and @code{__typeof__} continue to work despite
-@option{-ansi}.  You would not want to use them in an ISO C program, of
-course, but it is useful to put them in header files that might be included
-in compilations done with @option{-ansi}.  Alternate predefined macros
-such as @code{__unix__} and @code{__vax__} are also available, with or
-without @option{-ansi}.
-
-The @option{-ansi} option does not cause non-ISO programs to be
-rejected gratuitously.  For that, @option{-Wpedantic} is required in
-addition to @option{-ansi}.  @xref{Warning Options}.
-
-The macro @code{__STRICT_ANSI__} is predefined when the @option{-ansi}
-option is used.  Some header files may notice this macro and refrain
-from declaring certain functions or defining certain macros that the
-ISO standard doesn't call for; this is to avoid interfering with any
-programs that might use these names for other things.
-
-Functions that are normally built in but do not have semantics
-defined by ISO C (such as @code{alloca} and @code{ffs}) are not built-in
-functions when @option{-ansi} is used.  @xref{Other Builtins,,Other
-built-in functions provided by GCC}, for details of the functions
-affected.
-
 @opindex std
 @item -std=
 Determine the language standard. @xref{Standards,,Language Standards