[PATCH] Cygwin: doc: Fix type mismatch in porting.texi

Issue:newlib/libgloss/doc/porting.texi:570: warning: @ref node name should not contain `.'
      newlib/libgloss/doc/porting.texi:747: warning: @ref node name should not contain `.'
      newlib/libgloss/doc/porting.texi:938: warning: @ref node name should not contain `.'

reproduce:
git clone https://github.com/riscv-collab/riscv-gnu-toolchain.git
cd riscv-gnu-toolchain
./configure --prefix=`pwd`/install --with-arch=rv64gc --with-abi=lp64d --enable-multilib
make -j $(nproc)

The above issue will happen when executing the build command. This patch eliminates these warnings.
@ref{That},'That' does not contain node,so rename those sections names which don't contain '.'
refer:https://www.gnu.org/software/texinfo/manual/texinfo/texinfo.html#g_t_0040file
---
 libgloss/doc/porting.texi | 22 +++++++++++-----------
 1 file changed, 11 insertions(+), 11 deletions(-)

diff --git a/libgloss/doc/porting.texi b/libgloss/doc/porting.texi
index 15f214d02..5257e7f91 100644
--- a/libgloss/doc/porting.texi
+++ b/libgloss/doc/porting.texi
@@ -567,7 +567,7 @@ and then the ROM takes over. Pick a safe vector with no side
 effects. Some ROMs have a builtin trap handler just for this case.
 @end enumerate
 portable between all the m68k based boards we have here.
-@ref{crt0.S,,Example Crt0.S}. 
+@ref{CRT0S,,Example Crt0.S}.
 
 
 @smallexample
@@ -744,7 +744,7 @@ check a few critical addresses like @code{start}, @code{bss_end}, and
 
 Here's a breakdown of a linker script for a m68k based target board.
 See the file @code{libgloss/m68k/idp.ld}, or go to the appendixes in
-the end of the manual. @ref{idp.ld,,Example Linker Script}. 
+the end of the manual. @ref{IDPLD,,Example Linker Script}.
 
 @smallexample
 STARTUP(crt0.o)
@@ -935,7 +935,7 @@ sbrk(). @code{malloc()}, @code{calloc()}, and @code{realloc()} all call
 @code{sbrk()} at there lowest level. @code{caddr_t} is defined elsewhere
 as @code{char *}. @code{RAMSIZE} is presently a compile time option. All
 this does is move a pointer to heap memory and check for the upper
-limit. @ref{glue.c,,Example libc support code}. @code{sbrk()} returns a
+limit. @ref{GLUEC,,Example libc support code}. @code{sbrk()} returns a
 pointer to the previous value before more memory was allocated.
 
 @smallexample
@@ -1403,19 +1403,19 @@ as an ascii file, or using @code{xmodem}.
 
 @node Binutils, Code Listings, GDB, Top
 
-@node Code Listings, idp.ld, Binutils, Top
+@node Code Listings, IDPLD, Binutils, Top
 @appendix Code Listings
 
 @menu
-* idp.ld::              A m68k linker script.
-* crt0.S::              Crt0.S for an m68k.
-* glue.c::              C based support for for Stdio functions.
+* IDPLD::              A m68k linker script.
+* CRT0S::              Crt0.S for an m68k.
+* GLUEC::              C based support for for Stdio functions.
 * mvme.S::              Rom monitor based I/O support in assembler.
 * io.c::                C based for memory mapped I/O.
 * leds.c::              C based LED routines.
 @end menu
 
-@node idp.ld, crt0.S, Code Listings, Code Listings
+@node IDPLD, CRT0S, Code Listings, Code Listings
 @section Linker script for the IDP board
 
 This is the linker script script that is used on the Motorola IDP board.
@@ -1490,7 +1490,7 @@ SECTIONS
 @}
 @end example
 
-@node crt0.S, glue.c, idp.ld, Code Listings
+@node CRT0S, GLUEC, IDPLD, Code Listings
 @section crt0.S - The startup file
 
 @example
@@ -1605,7 +1605,7 @@ SYM (exit):
 	trap	#0
 @end example
 
-@node glue.c, mvme.S, crt0.S, Code Listings
+@node GLUEC, mvme.S, CRT0S, Code Listings
 @section C based "glue" code.
 
 @example
@@ -1838,7 +1838,7 @@ unsigned int num;
 @}
 @end example
 
-@node mvme.S, io.c, glue.c, Code Listings
+@node mvme.S, io.c, GLUEC, Code Listings
 @section I/O assembler code sample
 
 @example
-- 
2.17.1