Change counter to uint8_t; fix start index
Add function to calc search space coverage
Make newline after print_input() optional
Allow setting of starting hash
Add function to calc and print ETA
Refactor print_input() to print_sha()
Move printing start vals after processing args
Add specification of target SHA
Add notice when actually finding a fixpoint
Add report header and switch for it
Add actual help output with -h switch
Fix output executable name and *.d files
Handle SIGINT and print report/info when exiting
Include Git revision as version

Updated Makefile and main.c to include a git version string if the program is
compiled within a git repository. The version string will be formatted like
"git:<rev>" where <rev> is the output of `git describe --always --tags`. If
`git describe` doesn't return anything (as is the case when we're not in a Git
repo), the version string is empty and will not be included in the compilation.

If the version string is passed to the program by a defined called GITVERSiON
(must be a quoted string), it will be compiled and printed on the help page
(when the program is called like `./stablefinder -h`). That define can be
entered on the compiler's command line (as happens in the Makefile) or defined
in some external file that gets included in main.c.
Add switch to set report frequency
Make sure start param is printed on exit
Add optimization and use CC from env
Fix sha1 call to actually do something

Since a very early revision, the call to sha1_buffer() used a buffer length
argument of '0' (where obviously it should have been 20), because of which the
function would always return the same hash. As we have not previously looked at
the actual return values of the function, we hadn't noticed this before.
Fix main loop to check starting SHA too

The previously used structure of the main loop would increment the input value
before checking it, which would always skip the starting SHA. While this was not
a problem for starting at 0 (of which we know it is not a fixpoint), it would
have been easy to overlook certain SHAs when starting at other ranges.
Fix endianness of input array

Our sha1_buffer function returns the output buffer in byte-wise little-endian
order; in order for our comparison of input and output (memcmp) to work
correctly, our input array has to use the same order.
Thus I fixed all parts of the code touching any of the SHA arrays (e.g. string
to sha, print sha, increment input, etc) to conform with this new little-endian
order.