Fix strict-warnings build

crypto/asn1/a_strex.c: Type of width variable in asn1_valid_host
function  needs to be changed from char to signed char to avoid
build error due to '-Werror=type-limits'.
Signed-off-by: NPatrick Steuer <psteuer@mail.de>
Reviewed-by: NRich Salz <rsalz@openssl.org>
Reviewed-by: NRichard Levitte <levitte@openssl.org>
Reviewed-by: NMatt Caswell <matt@openssl.org>
CLA: trivial

crypto/asn1/a_strex.c

@@ -601,7 +601,7 @@ int asn1_valid_host(const ASN1_STRING *host)
     const unsigned char *hostptr = host->data;
     int type = host->type;
     int i;
-    char width = -1;
+    signed char width = -1;
     unsigned short chflags = 0, prevchflags;
 
     if (type > 0 && type < 31)