Change pseudorandom string generation

Use LC_ALL instead of LC_CTYPE to fix an issue with tr not recognizing
some characters outputed by /dev/urandom
Use [:alnum:] instead of '0-9' to get all alphanumeric characters
Increase string size from 24 to 32

Author: Victor Bouvier-Deleau

format_email.sh

@@ -8,7 +8,7 @@
 
 # Usage: format_email "Subject" "address@example.com" /path/to/body.html [/path/to/attachment.ext] | sendmail -i -t
 format_email () {
-  email_boundary=$(LC_CTYPE=C tr -dc '0-9' < /dev/urandom | head -c 24)
+  email_boundary=$(LC_ALL=C tr -dc '[:alnum:]' < /dev/urandom | head -c 32)
 
   echo "MIME-Version: 1.0"
   echo "Subject: ${1}"