Increase version number to 0.3.7

Signed-off-by: Antonio Niño Díaz <[email protected]>

Increase version number to 0.3.6

Signed-off-by: Antonio Niño Díaz <[email protected]>

Increase version number to 0.3.5

Signed-off-by: Antonio Niño Díaz <[email protected]>

Fix typo in documentation

Signed-off-by: Antonio Niño Díaz <[email protected]>

Improve error messages

Signed-off-by: Antonio Niño Díaz <[email protected]>

Fail when using negative constants if not allowed

Some commands, such as `DS`, `BANK[n]`, etc, don't allow the use of
negative constants, but there wasn't any check to prohibit the code from
trying to do so.

This patch adds the `uconst` type to the parser to use when a constant
is expected, but it mustn't be negative.

Signed-off-by: Antonio Niño Díaz <[email protected]>

Make fatalerror and yyerror consistent

There are two ways in which the assembly process can fail:

1. If there is a really big problem that compromises the whole process,
   the assembler has to stop right there and generate an error message.
   This happens with unterminated REPT loops, macros, etc.

2. If the problem isn't that big and the process can still continue,
   even though the final result is invalid, the assembler can try to
   continue and warn the user about all errors it finds in the code.

This patch clarifies the use of each function and replaces the function
used in two places by the correct one.

Signed-off-by: Antonio Niño Díaz <[email protected]>

Improve MinGW target of Makefile

It works now with an install of MinGW for both Win32 and Win64. It needs
libpng and zlib.

Signed-off-by: Antonio Niño Díaz <[email protected]>

Merge pull request gbdev#16 from yenatch/eval-rpn-bank

rgbasm: Evaluate BANK() arguments to verify they exist.

Tag rgbds-0.2.4.