Complete the prototype removal in ca1431.
The script prevents SWIGTOOL=gdb from working as gdb can't be used to
debug a shell script, it requires a binary.
Add support for SWIGTOOL in all the examples.
SWIG_LIB_DIR and SWIGEXE must now instead be set by all Makefiles.
See issue #473.
Turns out the issue that led me to push a broken commit in
the first place also caused the build to succeed when I
tested the fix in a rush. I should've just used the GitHub
merge button. Sorry for the noise, hopefully won't happen again.
