Implement a '#' prefix for raw identifiers that may alias keywords (#1480)

* Implement a '#' prefix for raw identifiers that may alias keywords

* Review comments

* Disallow hashless raw identifiers in interpolations

* Run clang-format

test/asm/empty-raw-identifier.asm

@@ -0,0 +1,5 @@
+MACRO #macro
+	println "all args: \#"
+	println "bad args: \<?>, \<#>"
+ENDM
+	#macro a, #b, c, 1, #2, 3

test/asm/empty-raw-identifier.err

@@ -0,0 +1,5 @@
+error: empty-raw-identifier.asm(5) -> empty-raw-identifier.asm::macro(3):
+    Invalid character in bracketed macro argument '?'
+error: empty-raw-identifier.asm(5) -> empty-raw-identifier.asm::macro(3):
+    Empty raw symbol in bracketed macro argument
+error: Assembly aborted (2 errors)!

test/asm/empty-raw-identifier.out

@@ -0,0 +1,2 @@
+all args: a,#b,c,1,#2,3
+bad args: >, >

test/asm/interpolation.asm

@@ -27,3 +27,6 @@ PRINTLN "label {label}"
 MACRO foo
 ENDM
 PRINTLN "foo {foo}"
+
+; hashless keyword
+PRINTLN "xor {xor}"

test/asm/interpolation.err

@@ -4,4 +4,6 @@ error: interpolation.asm(22):
     Interpolated symbol "label" does not exist
 error: interpolation.asm(29):
     Interpolated symbol "foo" is not a numeric or string symbol
-error: Assembly aborted (3 errors)!
+error: interpolation.asm(32):
+    Interpolated symbol "xor" is a reserved keyword; add a '#' prefix to use it as a raw symbol
+error: Assembly aborted (4 errors)!

test/asm/interpolation.out

@@ -3,3 +3,4 @@ undef
 label 
 label $7E
 foo 
+xor 

test/asm/raw-identifiers.asm

@@ -0,0 +1,36 @@
+def #DEF equ 1
+def #def equ 2
+def #ghi equ 3
+export #def, #ghi
+
+def #align = 0
+def #rb rb #def
+
+MACRO #macro
+	println "\<#def> is not \<#DEF>"
+ENDM
+	#macro first, second
+	purge #macro
+	assert !def(#macro)
+
+section "section", rom0
+#section::
+	dw #section
+#.rom0:
+	db BANK(#section.rom0)
+#section.romx:
+	println "section.romx is in ", SECTION(.romx)
+
+def #sub equs "def"
+{#sub} #add equs "#"
+
+for #for, {{#add}{#sub}}
+	println "for == ", #for
+endr
+	assert #for == 2
+	assert !{#sub}(#FOR)
+
+	newcharmap #charmap, #main
+	charmap "#", $42
+	setcharmap #charmap
+	db "#"

test/asm/raw-identifiers.out

@@ -0,0 +1,4 @@
+second is not first
+section.romx is in section
+for == $0
+for == $1