use file:line:col as key for the xref dict

Signed-off-by: Adrian Negreanu <adrian.m.negreanu@intel.com>
extract docs and use xrefs key
compiler script

Signed-off-by: Adrian Negreanu <adrian.m.negreanu@intel.com>
sqlite3: fedora has libsqlite3.so in /usr/lib64

Signed-off-by: Adrian Negreanu <groleo@gmail.com>