Strip UTF-8 BOM from source input and stdin (closes #225)

UTF-8 BOM being unhandled was the cause of the nine failing tests.

Author: python-processing-unit

src/builtins.c

@@ -7515,6 +7515,11 @@ static Value builtin_input(Interpreter *interp, Value *args, int argc, Expr **ar
     char buf[4096];
     if (fgets(buf, sizeof(buf), stdin) != NULL) {
         size_t len = strlen(buf);
+        if (len >= 3 && (unsigned char)buf[0] == 0xEF && (unsigned char)buf[1] == 0xBB &&
+            (unsigned char)buf[2] == 0xBF) {
+            memmove(buf, buf + 3, len - 2);
+            len -= 3;
+        }
         if (len > 0 && buf[len - 1] == '\n') {
             buf[len - 1] = '\0';
         }

src/lexer.c

@@ -88,6 +88,11 @@ void lexer_init(Lexer *lexer, const char *source, const char *filename) {
     lexer->current = 0;
     lexer->line = 1;
     lexer->column = 1;
+    if (lexer->source_len >= 3 && (unsigned char)lexer->source[0] == 0xEF && (unsigned char)lexer->source[1] == 0xBB &&
+        (unsigned char)lexer->source[2] == 0xBF) {
+        lexer->source += 3;
+        lexer->source_len -= 3;
+    }
 }
 
 char *lexer_get_line(Lexer *lexer, int line_num) {