fix permissions on include directory
fix permissions on include directory

Installing a library shouldn't grant world write permissions on the
include directory.  Write for owner and read (execute for directories)
for everyone else is sufficient and safe.

philipp-cliqz/milagro-crypto-c,miracl/milagro-crypto-c,milagro-crypto/milagro-crypto-c,philipp-cliqz/milagro-crypto-c,miracl/milagro-crypto-c,milagro-crypto/milagro-crypto-c,philipp-cliqz/milagro-crypto-c,milagro-crypto/milagro-crypto-c,miracl/milagro-crypto-c,miracl/milagro-crypto-c,miracl/milagro-crypto-c,philipp-cliqz/milagro-crypto-c,milagro-crypto/milagro-crypto-c