Implement -Wtruncation=level (#931)

* Implement -Wtruncation=level

-Wtruncation=0 is the same as the current -Wno-truncation.
-Wtruncation=2 is the same as the current -Wtruncation.
-Wtruncation=1 is the new default; it's less strict, allowing
N-bit values to be between -2**N and 2**N (exclusive).

* Implement generic "parametrized warning" system

* Test more `Wtruncation` variants

Co-authored-by: ISSOtm <eldredhabert0@gmail.com>

test/asm/warn-truncation.asm

@@ -0,0 +1,38 @@
+FOO_F EQU 5
+BAR_F EQU 7
+
+
+SECTION "RAM", WRAMX[$d500]
+
+wLabel::
+
+
+SECTION "ROM", ROM0
+
+MACRO try
+	OPT \1
+	; no warning
+	db 1 << FOO_F
+	db $ff ^ (1 << FOO_F)
+	db ~(1 << FOO_F)
+	db 1 << BAR_F
+	db $ff ^ (1 << BAR_F)
+	dw wLabel
+	dw $10000 - wLabel
+	; warn at level 1
+	db 1 << 8
+	db ~(1 << 8)
+	dw $1d200
+	dw -$1d200
+	; warn at level 2
+	db ~(1 << BAR_F)
+	dw -wLabel
+ENDM
+
+	try Wno-truncation
+	try Wtruncation
+	try Wtruncation=0
+	try Wtruncation=1
+	try Wtruncation=2
+	try Werror=truncation=1
+	try Werror=truncation=2