Request: support -L option like cscope

[RobPellowski]

The -L option is useful for streaming/offline operation.

From cscope documentation:

-L
Do a single search with line-oriented output when used with the -num pattern option.

Example:
pycscope.py -L3myfunction
Finds functions calling myfunction

Options that cscope supports:

     n  cscope operation
    --- ---------------------------------------
     0  Find this C symbol:
     1  Find this function definition:
     2  Find functions called by this function:
     3  Find functions calling this function:
     4  Find this text string:
     5  Change this text string:
     6  Find this egrep pattern:
     7  Find this file:
     8  Find files #including this file:
     9  Find assignments to this symbol: