Parse GHDL diagnostic severity

[JennToo]

GHDL provides the severity of its diagnostics. For example:

test/tb_lfsr.vhd:7:20:error: no declaration for "std_logic"
    signal clk   : std_logic;
                   ^
test/tb_lfsr.vhd:8:20:error: no declaration for "std_logic"
    signal arst  : std_logic;
                   ^
test/tb_lfsr.vhd:9:20:error: no declaration for "std_logic_vector"
    signal value : std_logic_vector(15 downto 0);
                   ^
test/tb_lfsr.vhd:7:12:warning: signal "clk" is never referenced [-Wunused]
    signal clk   : std_logic;
           ^
test/tb_lfsr.vhd:8:12:warning: signal "arst" is never referenced [-Wunused]
    signal arst  : std_logic;
           ^
test/tb_lfsr.vhd:9:12:warning: signal "value" is never referenced [-Wunused]
    signal value : std_logic_vector(15 downto 0);

I don't know if it will ever produce any other kind of severity. But these two seem to be the most common.