tools: install gdbinit from v8 to $PREFIX/share
gdbinit provided by V8 can be very useful for low-level debugging of crashes in node and in binary addons. Most useful commands at 'jst' for JS stack traces and 'job' for printing a heap object.
This patch installs the file at $PREFIX/share/tools/gdbinit making it available on installed Node.js binaries too.
Here's a sample session that uses these gdb macros: https://gist.github.com/ofrobots/0bdcab89771221ace68d