fix date literal bugs + add more date literal tests (#1132)

Changes:
1. Case handled incorrectly when L/M is month name and other L/M is year
2. JULY was missing
3. Problem with creating single letter tokens
4. Introduced dateValueNumber in order to make null checks instead of .Count > 0 possible for testing whether the date part is a number or name

Author: Andrin Meier

Rubberduck.Parsing/Grammar/VBA.g4

@@ -845,12 +845,36 @@ fragment DATEVALUE : DATEVALUEPART DATESEPARATOR DATEVALUEPART (DATESEPARATOR DA
 fragment DATEVALUEPART : DIGIT+ | MONTHNAME;
 fragment DATESEPARATOR : WS? [/,-]? WS?;
 fragment MONTHNAME : ENGLISHMONTHNAME | ENGLISHMONTHABBREVIATION;
-fragment ENGLISHMONTHNAME : J A N U A R Y | F E B R U A R Y | M A R C H | A P R I L | M A Y | J U N E  | A U G U S T | S E P T E M B E R | O C T O B E R | N O V E M B E R | D E C E M B E R;
-fragment ENGLISHMONTHABBREVIATION : J A N | F E B | M A R | A P R | J U N | J U L | A U G | S E P |  O C T | N O V | D E C;
+fragment ENGLISHMONTHNAME : JANUARY | FEBRUARY | MARCH | APRIL | MAY | JUNE | JULY | AUGUST | SEPTEMBER | OCTOBER | NOVEMBER | DECEMBER;
+fragment ENGLISHMONTHABBREVIATION : JAN | FEB | MAR | APR | JUN | JUL | AUG | SEP | OCT | NOV | DEC;
 fragment TIMEVALUE : DIGIT+ AMPM | DIGIT+ TIMESEPARATOR DIGIT+ (TIMESEPARATOR DIGIT+)? AMPM?;
 fragment TIMESEPARATOR : WS? (':' | '.') WS?;
 fragment AMPM : WS? (A M | P M | A | P);
 
+JANUARY : J A N U A R Y;
+FEBRUARY : F E B R U A R Y;
+MARCH : M A R C H;
+APRIL : A P R I L;
+MAY : M A Y;
+JUNE : J U N E;
+JULY : J U L Y;
+AUGUST : A U G U S T;
+SEPTEMBER : S E P T E M B E R;
+OCTOBER : O C T O B E R;
+NOVEMBER : N O V E M B E R;
+DECEMBER : D E C E M B E R;
+JAN : J A N;
+FEB : F E B;
+MAR: M A R;
+APR : A P R;
+JUN : J U N;
+JUL: J U L;
+AUG : A U G;
+SEP : S E P;
+OCT : O C T;
+NOV : N O V;
+DEC : D E C;
+
 // whitespace, line breaks, comments, ...
 LINE_CONTINUATION : [ \t]+ UNDERSCORE '\r'? '\n' -> skip;
 NEWLINE : [\r\n\u2028\u2029]+;

Rubberduck.Parsing/Grammar/VBALexer.cs

@@ -74,12 +74,35 @@ fragment DATEVALUE : DATEVALUEPART DATESEPARATOR DATEVALUEPART (DATESEPARATOR DA
 fragment DATEVALUEPART : DIGIT+ | MONTHNAME;
 fragment DATESEPARATOR : WS? [/,-]? WS?;
 fragment MONTHNAME : ENGLISHMONTHNAME | ENGLISHMONTHABBREVIATION;
-fragment ENGLISHMONTHNAME : J A N U A R Y | F E B R U A R Y | M A R C H | A P R I L | M A Y | J U N E  | A U G U S T | S E P T E M B E R | O C T O B E R | N O V E M B E R | D E C E M B E R;
-fragment ENGLISHMONTHABBREVIATION : J A N | F E B | M A R | A P R | J U N | J U L | A U G | S E P |  O C T | N O V | D E C;
+fragment ENGLISHMONTHNAME : JANUARY | FEBRUARY | MARCH | APRIL | MAY | JUNE | JULY | AUGUST | SEPTEMBER | OCTOBER | NOVEMBER | DECEMBER;
+fragment ENGLISHMONTHABBREVIATION : JAN | FEB | MAR | APR | JUN | JUL | AUG | SEP | OCT | NOV | DEC;
 fragment TIMEVALUE : (DIGIT+ AMPM) | (DIGIT+ TIMESEPARATOR DIGIT+ (TIMESEPARATOR DIGIT+)? AMPM?);
 fragment TIMESEPARATOR : WS? (':' | '.') WS?;
 fragment AMPM : WS? (A M | P M | A | P);
 
+JANUARY : J A N U A R Y;
+FEBRUARY : F E B R U A R Y;
+MARCH : M A R C H;
+APRIL : A P R I L;
+MAY : M A Y;
+JUNE : J U N E;
+JULY : J U L Y;
+AUGUST : A U G U S T;
+SEPTEMBER : S E P T E M B E R;
+OCTOBER : O C T O B E R;
+NOVEMBER : N O V E M B E R;
+DECEMBER : D E C E M B E R;
+JAN : J A N;
+FEB : F E B;
+MAR: M A R;
+APR : A P R;
+JUN : J U N;
+JUL: J U L;
+AUG : A U G;
+SEP : S E P;
+OCT : O C T;
+NOV : N O V;
+DEC : D E C;
 NOT : N O T;
 TRUE : T R U E;
 FALSE : F A L S E;