utf8 in identifiers

made like in pcc
    (pcc.ludd.ltu.se/ftp/pub/pcc-docs/pcc-utf8-ver3.pdf)
    We treat all chars with high bit set as alphabetic.
    This allow code like

    #include <stdio.h>
    int Lefèvre=2;
    int main() {
        printf("Lefèvre=%d\n",Lefèvre);
        return 0;
    }

tests/tests2/83_utf8_in_identifiers.expect

@@ -0,0 +1,2 @@
+привет=0.1
+Lefèvre=2