Documentation: add missing quotes to "git grep" examples

Without an indication to the contrary, Asciidoc puts 'quoted text' in italics, making the output look like this: git grep time_t -- *.[ch] Looks for time_t in all tracked .c and .h files in the working directory and its subdirectories. git grep -e '#define\' --and \( -e MAX_PATH -e PATH_MAX \) Looks for a line that has #define and either MAX_PATH or PATH_MAX. In the first example, the *.[ch] argument needs to be protected from the shell, or else it will only match files in the current directory. The second example has a stray backslash. Reported-by: Frédéric Brière <fbriere@fbriere.net> Cc: Mark Lodato <lodatom@gmail.com> Cc: Junio C Hamano <gitster@pobox.com> Signed-off-by: Jonathan Nieder <jrnieder@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>