fix: error and warning directives in zxbpp

When preprocessing asm files, the zxbpp error and
warning directives were not working. Fixed.

Author: boriel

src/zxbpp/zxbasmpplex.py

@@ -74,6 +74,8 @@
     "line": "LINE",
     "require": "REQUIRE",
     "pragma": "PRAGMA",
+    "error": "ERROR",
+    "warning": "WARNING",
 }
 
 # List of token names.

tests/functional/error_macro.asm

@@ -0,0 +1,4 @@
+#warning "this is a warning"
+#error "this is an error"
+nop
+

tests/functional/test_errmsg.txt

@@ -252,3 +252,7 @@ ND.Controls.bas:4: error: Invalid argument 'dirData'
 ND.Controls.bas:2: warning: [W150] Variable 'dirData' is never used
 >>> process_file('zx48k/bad_fname_err4.bas', ['-S', '-q'])
 ND.Controls.bas:2: error: sub 'Controls_LABEL' declared but not implemented
+
+>>> process_file('error_macro.asm')
+error_macro.asm:1: warning: this is a warning
+error_macro.asm:2: error: this is an error