[GSoC] Microproject: Add more builtin patterns for userdiff

Hi,

for the microproject: creating diff function support for different languages. i wrote one for shell script, have tested it outside of git and it works fine.

query regarding accommodating the pattern in:
1) userdiff.c, it uses - #define PATTERNS(name, pattern, word_regex),
for defining patterns to locate functions.
what is the use of pattern and word_regex parameters ? i am guessing
that pattern parameter is the actual pattern to spot functions in a
file,
and word_regex is used to get function name. is that correct ?
please let me know.