Added a .gitignore file to ignore the output of compilation.
Fix some warnings that GCC 4.7.2 alerted me to.  The warnings that I fixed are:

wmidump.c: In function ‘read_wdg’:
wmidump.c:261:15: warning: pointer of type ‘void *’ used in arithmetic [-pedantic]
wmidump.c: In function ‘main’:
wmidump.c:273:14: warning: unused parameter ‘argc’ [-Wunused-parameter]
wmidump.c:273:26: warning: unused parameter ‘argv’ [-Wunused-parameter]
wmidump.c: At top level:
wmidump.c:108:13: warning: ‘wmi_swap_bytes’ defined but not used [-Wunused-function]
wmidump.c:134:13: warning: ‘wmi_parse_guid’ defined but not used [-Wunused-function]