Add support for OAM Sections

Allows sections (and labels within) to be defined that correspond to the Game Boy’s Object Attributes Memory.

src/asm/globlex.c

@@ -342,6 +342,7 @@ struct sLexInitString staticstrings[] = {
 	{"hram", T_SECT_HRAM},
 	{"wramx", T_SECT_WRAMX},
 	{"sram", T_SECT_SRAM},
+	{"oam", T_SECT_OAM},
 
 	{NAME_RB, T_POP_RB},
 	{NAME_RW, T_POP_RW},