Fix removing parentheses when using deducing assignement (#331)

The issue is caused by `emit(expression_list_node)` that skips parentheses
when node is inside initializer - that serves cases like:
```cpp
v : std::vector<int> = (1,2,3);
```
Where it generates:
```cpp
std::vector<int> v{1,2,3};
```

When `:=` is used in the following cases:
```cpp
d := (1 + 2) * (3 + 4) * (5 + 6);
```
It removes first parentheses and we end up with:
```cpp
auto d = {1 + 2 * (3 + 4) * ( 5 + 6)};
```

This change corrects this behaviour on the parsing side. After parsing
expression list it checks if the next lexeme is `Semicolon`. If it is it
means that we are on the initializer of the form:
```cpp
d1 := ((2 + 1) * (4 - 1) * (8 - 3));
d3 := (move d2);
v : std::vector<int> = ();
```
And we can suppres printing of parentheses - as there will be braces:
```cpp
auto d1 {(2 + 1) * (4 - 1) * (8 - 3)};
auto d3 {std::move(d2)};
std::vector<int> v {};
```

When next lexeme is not `Semicolon` it means that we are in initializer
of the form:
```cpp
d2 := (2 + 1) * (4 - 1) * (8 - 3);
d4 : _ = (1 + 2) * (3 + 4) * (5 + 6);
d5 : int = (1 + 2) * (3 + 4) * (5 + 6);
```
And we need to keep all the parentheses and it will be generates to:
```cpp
auto d2 {(2 + 1) * (4 - 1) * (8 - 3)};
auto d4 {(1 + 2) * (3 + 4) * (5 + 6)};
int d5 {(1 + 2) * (3 + 4) * (5 + 6)};
```

Author: filipsajdak

source/parse.h

@@ -2852,7 +2852,9 @@ class parser
             //      || curr().type() == lexeme::LeftBrace
             )
         {
-            bool inside_initializer = (peek(-1)->type() == lexeme::Assignment);
+            bool inside_initializer = ( 
+                peek(-1) && peek(-1)->type() == lexeme::Assignment
+            );
             auto open_paren = &curr();
             auto close = close_paren_type(open_paren->type());
             auto close_text = [&] () -> std::string { if (close == lexeme::RightParen) { return ")"; } return "}"; }();
@@ -2870,6 +2872,9 @@ class parser
             }
             expr_list->close_paren = &curr();
             next();
+            if (curr().type() != lexeme::Semicolon) {
+                expr_list->inside_initializer = false;
+            } 
             n->expr = std::move(expr_list);
             return n;
         }