Add flag to rgbasm to disable LD->LDH optimization

rgbasm tries to optimize any loads from/to $FF00-$FFFF and generate
LDH 2-byte opcodes instead of regular LD 3-byte opcodes. This is a bit
inconsistent as it only works for constant values. If a load is trying
to access a label in a HRAM floating section, or a section found in a
different object file, this optimization doesn't work.

This means that a simple refactor or code could allow rgbasm to perform
the optimzation or prevent it from doing so. For certain projects, like
disassemblies, this is a problem.

This patch adds flag -L to rgbasm to disable the optimization, and
doesn't change the behaviour of any other existing code.

Signed-off-by: Antonio Niño Díaz <antonio_nd@outlook.com>

include/asm/main.h

@@ -15,12 +15,13 @@
 #include "extern/stdnoreturn.h"
 
 struct sOptions {
-	char gbgfx[4];
 	char binary[2];
-	int32_t fillchar;
-	bool verbose;
-	bool haltnop;
+	char gbgfx[4];
 	bool exportall;
+	int32_t fillchar;
+	bool haltnop;
+	bool optimizeloads;
+	bool verbose;
 	bool warnings; /* True to enable warnings, false to disable them. */
 };