Improve Pan language support (#3691)

* Add a larger set of sample files for Pan

This is a fairly good cross section of Pan based on code from:
* https://github.com/quattor/template-library-examples
* https://github.com/quattor/template-library-core

* Add Pan language grammar

samples/Pan/types.pan

@@ -0,0 +1,151 @@
+@contributor{
+  name = First Contributor
+  email = first@example.org
+}
+@contributor{
+  name = Second Contributor
+  email = second@example.org
+}
+@documentation{
+Data type and function definitions for basic types
+}
+
+declaration template pan/types;
+
+include 'pan/legacy';
+
+@documentation{
+This type implements a date/time format consistent with
+ASN.1 typically used by LDAP.  The actual specification is the
+"GeneralizedTime" format as specified on page 38 of the X.208
+ITU-T recommendation and references within.
+
+Ex: 20040825120123Z
+    20040825120123+0100
+    20040825120123,5
+    20040825120123.5
+    20040825120123.5-0123
+}
+function is_asndate = {
+    # Check cardinality and type of argument.
+    if (ARGC != 1 || !is_string(ARGV[0]))
+        error("usage: is_asndate(string)");
+
+    # Match the datetime pattern, extracting interesting fields.
+    result = matches(ARGV[0],
+        '^(\d{4})(\d{2})(\d{2})(\d{2})(\d{2})(\d{2})(?:[,\.](\d+))?([Zz]|(?:[-+]\d{2}\d{2}))?$');
+
+    if (length(result) >= 7) {
+        # Do further tests on various components of the date.
+        # NOTE: the to_long(to_double(x)) construct below is to avoid having
+        # the to_long function treat strings with leading zeros as octal
+        # numbers.  E.g. to_long("09") will throw an exception because '9' is
+        # not a valid octal digit.
+        year = to_long(result[1]);
+        month = to_long(to_double(result[2]));
+        day = to_long(to_double(result[3]));
+        hour = to_long(to_double(result[4]));
+        minute = to_long(to_double(result[5]));
+        second = to_long(to_double(result[6]));
+
+        frac = 0;
+        if (length(result) > 7) {
+            frac = to_long(to_double(result[7]));
+        };
+
+        zone = '+0000';
+        if (length(result) > 8) {
+            zone = result[8];
+        };
+
+        # Check the range of months.
+        if (month < 1 || month > 12) {
+            error("is_asndate: invalid month");
+            return(false);
+        };
+
+        # Check the range of days.
+        if (day < 1 || day > 31) {
+            error("is_asndate: invalid day");
+            return(false);
+        };
+
+        # Be more specific on the days in each month.
+        if (month == 4 || month == 6 || month == 9 || month == 11) {
+            if (day > 30) {
+                error("is_asndate: invalid day");
+            };
+        };
+
+        # February is always a bother.  Too lazy to check that the leap
+        # years have been specified correctly.
+        if (month == 2 && day > 29) {
+            error("is_asndate: invalid day");
+        };
+
+        # Check the time.
+        if (hour > 23) {
+            error("is_asndate: invalid hour");
+            return(false);
+        };
+        if (minute > 59) {
+            error("is_asndate: invalid minute");
+            return(false);
+        };
+
+        # Allow for leap seconds here (since it is easy).
+        if (second > 60) {
+            error("is_asndate: invalid minute");
+            return(false);
+        };
+
+        # Check the time zone format.
+        if (zone != "Z" && zone != "z") {
+            tz = matches(zone, '^[-+](\d{2})(\d{2})$');
+
+            hoffset = to_long(to_double(tz[1]));
+            moffset = to_long(to_double(tz[2]));
+
+            if (hoffset >= 12) {
+                error("is_asndate: invalid hour offset in time zone");
+                return(false);
+            };
+            if (moffset > 59) {
+                error("is_asndate: invalid minute offset in time zone");
+                return(false);
+            };
+        };
+
+    } else {
+        error("is_asndate: invalid format for time");
+        return(false);
+    };
+
+    # If it gets to this point, then the date must be OK.
+    true;
+};
+
+
+type type_asndate = string with {
+    is_asndate(SELF);
+};
+
+@documentation{
+    desc = Type that enforces the existence of a named interface.
+}
+type valid_interface = string with {
+    if (exists(format('/system/network/interfaces/%s', SELF))) {
+        return(true);
+    };
+    foreach(ifc; attr; value('/system/network/interfaces')) {
+        if (attr['device'] == SELF){
+            return(true);
+        };
+    };
+    false;
+};
+
+@documentation{
+    desc = CPU architectures understood by Quattor
+}
+type cpu_architecture = string with match (SELF, '^(i386|ia64|x86_64|sparc|aarch64|ppc64(le)?)$');