Globalize envmatch()

The newly introduced API (routines related to env vars) will need to call
it.

Signed-off-by: Rafal Zabdyr <armo@semihalf.com>

include/common.h

diff --git a/include/common.h b/include/common.h
index 493417f..da2f01b 100644
--- a/include/common.h
+++ b/include/common.h
@@ -227,6 +227,7 @@
 /* common/cmd_nvedit.c */
 int	env_init     (void);
 void	env_relocate (void);
+int	envmatch     (uchar *, int);
 char	*getenv	     (char *);
 int	getenv_r     (char *name, char *buf, unsigned len);
 int	saveenv	     (void);