portable: template: use as a subproject Move template into its own subproject as it's only needed at compile-time and shouldn't be installed. This needs compiling with the host compiler which is configurable via HOSTCC and HOSTCLFAG environment variables. This diff largely from op@ but additional tweaking from myself.

portable: template: don't install the binary template and its manpages it's only needed at build time to generate a source file.

portable: template: drop tmpl.c from SOURCES was added there mistakenly. it's not part of the "compiler", it's part of the "user library" and provides useful functions for the consumers. see also 1dec34dfda7ccb3caadab65aca907251ab8fd72e

portable: gotwebd: use template This updates -portable's gotwebd instance to make use of the new templating engine.