feature: Precedence macro name in PEG_TRACE

[A4-Tacks]

src/main.rs:

peg::parser!(grammar p() for str {
    rule number() -> f64 = s:$(['0'..='9']) { s.parse().unwrap() }
    pub rule preced() -> f64 = precedence! {
        a:(@) "+" b:@ { a+b }
        --
        a:(@) "*" b:@ { a*b }
        --
        n:number() { n }
        "(" e:preced() ")" { e }
    }
});

fn main() {
    let _ = dbg!(p::preced("1*2+3*4"));
}

Current output:

[PEG_TRACE] Attempting to match rule `preced` at 1:1
[PEG_TRACE] Attempting to match rule `number` at 1:1
[PEG_TRACE] Matched rule `number` at 1:1 to 1:2
[PEG_TRACE] Entering level 0
[PEG_TRACE] Attempting to match rule `number` at 1:3
[PEG_TRACE] Matched rule `number` at 1:3 to 1:4
[PEG_TRACE] Entering level 2
[PEG_TRACE] Leaving level 2
[PEG_TRACE] Attempting to match rule `number` at 1:5
[PEG_TRACE] Matched rule `number` at 1:5 to 1:6
[PEG_TRACE] Entering level 1
[PEG_TRACE] Attempting to match rule `number` at 1:7
[PEG_TRACE] Matched rule `number` at 1:7 to 1:8
[PEG_TRACE] Entering level 2
[PEG_TRACE] Leaving level 2
[PEG_TRACE] Leaving level 1
[PEG_TRACE] Leaving level 0
[PEG_TRACE] Matched rule `preced` at 1:1 to 1:8

Expect output:

[PEG_TRACE] Attempting to match rule `preced` at 1:1
[PEG_TRACE] Attempting to match rule `number` at 1:1
[PEG_TRACE] Matched rule `number` at 1:1 to 1:2
[PEG_TRACE] Entering rule `preced` level 0
[PEG_TRACE] Attempting to match rule `number` at 1:3
[PEG_TRACE] Matched rule `number` at 1:3 to 1:4
[PEG_TRACE] Entering rule `preced` level 2
[PEG_TRACE] Leaving rule `preced` level 2
[PEG_TRACE] Attempting to match rule `number` at 1:5
[PEG_TRACE] Matched rule `number` at 1:5 to 1:6
[PEG_TRACE] Entering rule `preced` level 1
[PEG_TRACE] Attempting to match rule `number` at 1:7
[PEG_TRACE] Matched rule `number` at 1:7 to 1:8
[PEG_TRACE] Entering rule `preced` level 2
[PEG_TRACE] Leaving rule `preced` level 2
[PEG_TRACE] Leaving rule `preced` level 1
[PEG_TRACE] Leaving rule `preced` level 0
[PEG_TRACE] Matched rule `preced` at 1:1 to 1:8

Manually enter the name, or obtain it from nearby rules?