[meson] use non string true/false
[meson] use non string true/false

muon (a meson reimplementation) errors as it does not support having a
string for a boolean type.

Signed-off-by: Rosen Penev <rosenp@gmail.com>

github: #120

lighttpd/lighttpd1.4,lighttpd/lighttpd1.4,gstrauss/lighttpd1.4,lighttpd/lighttpd1.4,lighttpd/lighttpd1.4,lighttpd/lighttpd1.4,gstrauss/lighttpd1.4,gstrauss/lighttpd1.4,gstrauss/lighttpd1.4,lighttpd/lighttpd1.4,gstrauss/lighttpd1.4,gstrauss/lighttpd1.4