gdb/fortran: Simplify handling of Fortran dot operations and keywords

gdb/fortran: Simplify handling of Fortran dot operations and keywords

Use strncasecmp to compare Fortran dot operations (like .AND.) and for
the keywords list.  This allows for some duplication to be removed
from the token arrays.  I've also performed whitespace cleanup around
the code I've changed.

I have added some tests to ensure that upper and lowercase dot
operations are correctly tested.  The keywords list remains always
lowercase for now.

There should be no user visible changes after this commit.

gdb/ChangeLog:

	* f-exp.y (struct token): Add comments.
	(dot_ops): Remove uppercase versions and the end marker.
	(f77_keywords): Likewise.
	(yylex): Use ARRAY_SIZE to iterate over dot_ops, assert all
	entries in the dot_ops array are case insensitive, and use
	strncasecmp to compare strings.  Also some whitespace cleanup in
	this area.  Similar for the f77_keywords array, except entries in
	this list might be case sensitive.

gdb/testsuite/ChangeLog:

	* gdb.fortran/dot-ops.exp: New file.