Add a memstart symbol to the linkerscript

This replaces the old way of appending the memory bitmap to the end of the kernel, which started causing problems with expansion..

I hardcoded the value to 0x1440, which is the start of the first FREE block of memory given to SeaBIOS in QEMU. This should be changed in the future..

chroma/inc/kernel/system/memory.h

@@ -199,6 +199,8 @@ void* AlignPointer(const void* Pointer, size_t Alignment);
 *      C h r o m a    M e m o r y   M a n a g e m e n t
 *************************************************************/
 
+extern size_t memstart;
+
 extern size_t end;
 
 void        ListMemoryMap();

linker.ld

@@ -1,6 +1,7 @@
 
-mmio = 0xfffffffff8000000;
-fb   = 0xfffffffffc000000;
+memstart = 0x14400;
+mmio     = 0xfffffffff8000000;
+fb       = 0xfffffffffc000000;
 
 PHDRS
 {