Line up GCC __attribute__() tags
Change to use pkg-config

Looks like some of these libraries use the pkg-config database to
store the location they've been dumped. Not the best solution but
probably the only one that will work considering the arrogance of
some of these people.
Fix c&p bug
Add pkgconf configuration for the tcl library.

I've assumed that the tcl subdirectory for the include path will be
supplied by pkgconf as usual.
Move install command to variable (broken tcc)
Better GNU Lightning version detection

Also hunt for GCC simulating compilers so I know it's okay to add
the GCC flags (some of them)
Find GCC simulating compilers
Lightning works on woody
Add -fintio and update help.

The -fintio gives integer I/O on the jit runners and output on the C code.

The help now describes all the -f* options.
Small cleanup