Merge pull request #387 from ISSOtm/set_doesnt_override_equ

Prevent `SET` from overriding constant symbols

test/asm/symbol-override.asm

@@ -0,0 +1,14 @@
+V set 0
+V set 1
+    PRINTT "V={V}\n"
+
+W equ 1
+W set 0
+
+rsset 1
+X rb 0
+X set 0
+
+SECTION "Test", ROM0[1]
+Y:
+Y set 0

test/asm/symbol-override.out

@@ -0,0 +1,8 @@
+ERROR: symbol-override.asm(6):
+    'W' already defined as constant at symbol-override.asm(5)
+ERROR: symbol-override.asm(10):
+    'X' already defined as constant at symbol-override.asm(9)
+ERROR: symbol-override.asm(14):
+    'Y' already defined as non-constant at symbol-override.asm(13)
+error: Assembly aborted (3 errors)!
+V=$1

test/asm/symbol-override.out.pipe

@@ -0,0 +1,8 @@
+ERROR: -(6):
+    'W' already defined as constant at -(5)
+ERROR: -(10):
+    'X' already defined as constant at -(9)
+ERROR: -(14):
+    'Y' already defined as non-constant at -(13)
+error: Assembly aborted (3 errors)!
+V=$1