unicorn_http_common.rl: use only ASCII spaces for compatibility
Ragel 6.10 on FreeBSD 12.4 amd64 complains and fails on this, yet the same
Ragel version on Debian 11.x i386 and amd64 never has. I suspect this can
fix compatibility on s390x, arm64, armel, and armhf Debian builds:
https://buildd.debian.org/status/fetch.php?pkg=unicorn&arch=s390x&ver=6.1.0-1&stamp=
1687156375&file=log
https://buildd.debian.org/status/fetch.php?pkg=unicorn&arch=arm64&ver=6.1.0-1&stamp=
1687156478&file=log
https://buildd.debian.org/status/fetch.php?pkg=unicorn&arch=armel&ver=6.1.0-1&stamp=
1687156619&file=log
https://buildd.debian.org/status/fetch.php?pkg=unicorn&arch=armhf&ver=6.1.0-1&stamp=
1687156807&file=log
Fixes:
d5fbbf547203061b (Add some tolerance (RFC2616 sec. 19.3), 2016-10-20)