[Toybox] [PATCH v2]diff and patch: support special characters in filenames with quoting as well as unusual timestamp formats

[William Haddon]

After further research and testing, I've produced a patch which handles 
all filenames with special characters by copying the GNU quoting 
behavior, and also treats anything following a tab as a timestamp. This 
increases both ability to handle possible filenames and ability to 
apply patches found in the field.

Specifically, diff quotes and escapes filenames according to the 
following rules.
* Surround the filename with quotes if it contains a byte less than 
0x20, a byte greater than or equal to 0x80, space, backslash, or quote.
* Replace alert, backspace, form feed, newline, carriage return, tab, 
vertical tab, backslash, and quote with \a, \b, \f, \n, \r, \t, \v, \\, 
and \", respectively.
* Replace other bytes less than 0x20 or greater than or equal to 0x80 
with a backslash followed by the three octal digits representing the 
value of the byte.
* Treat valid UTF-8 characters involving sequences of bytes greater 
than or equal to 0x80 the same as other sequences of such bytes.

patch processes quoted and escaped filenames according to the following 
rules.
* If the filename does not begin with a quote, do not modify the 
filename.
* Remove quotes surrounding the filename.
* In quoted filenames, replace \a, \b, \f, \n, \r, \t, \v, \\, and \" 
with alert, backspace, form feed, newline, carriage return, tab, 
vertical tab, backslash, and quote, respectively.
* In quoted filenames, replace a backslash followed by octal digits 
with the byte with that value in octal.
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