Make linux kernel string funcs available to tools

isspace() and strim() are not in the typical user-mode string.h, so
put them in a separate compilation unit so that they can be built into
tools that need them independent of the other common string functions.

This allows code shared by u-boot and the linux user-mode tools to link.

Signed-off-by: Joe Hershberger <joe.hershberger@ni.com>

include/linux/string.h

@@ -50,10 +50,7 @@ extern char * strchr(const char *,int);
 #ifndef __HAVE_ARCH_STRRCHR
 extern char * strrchr(const char *,int);
 #endif
-extern char * skip_spaces(const char *);
-
-extern char *strim(char *);
-
+#include <linux/linux_string.h>
 #ifndef __HAVE_ARCH_STRSTR
 extern char * strstr(const char *,const char *);
 #endif