Fix --without-headers for sh targets

[Mike Frysinger <vapier at gentoo dot org>]

find attached a minor patch to fix building gcc-3.4 for sh targets and using 
the --without-headers configure option

verified gcc-3.4.3 was broken as is the gcc-3.4-20050401 snapshot ... and cvs 
shows that the gcc-3_4-branch could still use this

for reference, method to reproduce:
$ tar jxf binutils-2.15.94.0.1.tar.bz2 -C ~/
$ cd ~/binutils-2.15.94.0.1
$ ./configure --prefix=/usr/local --target=sh-linux
$ make
$ sudo make install
$ tar jxf gcc-3.4-20050401.tar.bz2 -C ~/
$ cd ~/gcc-3.4-20050401
$ /configure --target=sh-linux --disable-werror --enable-languages=c 
--disable-shared --disable-threads --without-headers
$ make
/home/vapier/gcc-3.4-20050401/gcc/xgcc -B/home/vapier/gcc-3.4-20050401/gcc/ 
-B/usr/local/sh-linux/bin/ -B/usr/local/sh-linux/lib/ 
-isystem /usr/local/sh-linux/include -isystem /usr/local/sh-linux/sys-include 
-O2  -DIN_GCC -DCROSS_COMPILE   -W -Wall -Wwrite-strings -Wstrict-prototypes 
-Wmissing-prototypes -Wold-style-definition  -isystem ./include  -fpic 
-DNO_FPSCR_VALUES -g  -DIN_LIBGCC2 -D__GCC_FLOAT_NOT_NEEDED -Dinhibit_libc 
-I. -I. -I. -I./. -I./../include   -DL_muldi3 -c ./libgcc2.c -o 
libgcc/./_muldi3.o
In file included from ./tm.h:10,
                 from ./libgcc2.c:43:
./config/sh/linux.h:149:20: signal.h: No such file or directory
./config/sh/linux.h:150:26: sys/ucontext.h: No such file or directory
make[2]: *** [libgcc/./_muldi3.o] Error 1
-mike

--- gcc/config/sh/linux.h
+++ gcc/config/sh/linux.h
@@ -154,6 +154,7 @@
 /* Do code reading to identify a signal frame, and set the frame
    state data appropriately.  See unwind-dw2.c for the structs.  */
 
+#ifndef inhibit_libc
 #ifdef IN_LIBGCC2
 #include <signal.h>
 #include <sys/ucontext.h>
@@ -304,6 +305,7 @@
 
 #endif /* defined (__SH5__) */
 #endif /* IN_LIBGCC2 */
+#endif /* inhibit_libc */
 
 /* For SH3 and SH4, we use a slot of the unwind frame which correspond
    to a fake register number 16 as a placeholder for the return address