Consistently do & alignMask, not % alignSize

Also add more unrelated tests for coverage

test/link/section-fragment/align-conflict.asm

@@ -0,0 +1,10 @@
+IF !DEF(SECOND)
+	def ATTRS equs ",ALIGN[2]"
+ELSE
+	def ATTRS equs "[$1337]"
+ENDC
+
+SECTION FRAGMENT "conflicting alignment", ROM0 {ATTRS}
+	db
+
+	PURGE ATTRS

test/link/section-fragment/align-conflict.out

@@ -0,0 +1,10 @@
+FATAL: Section "conflicting alignment" is defined with 4-byte alignment (offset 0), but also with address $1337
+    at section-fragment/align-conflict.asm(7)
+    and also:
+    at section-fragment/align-conflict.asm(7)
+Linking aborted with 1 error
+---
+error: Section already declared as aligned to 4 bytes (offset 0)
+    at <stdin>(18)
+FATAL: Cannot create section "conflicting alignment" (1 error)
+    at <stdin>(18)