Replaced builtin linker configs with ordinary .cfg files.

The benefits are:
- Independency of ld65 build from perl
- More transparent behaviour

cfg/lunix.cfg

@@ -0,0 +1,44 @@
+# ld65 Linker-configuration for LUnix, Next Generation.
+
+SYMBOLS {
+    __HEAPSIZE__:  type = weak, value = $2000; # 8k heap [temporary, until LUnix malloc() exists]
+    __STACKSIZE__: type = weak, value = $0400; # 1k stack (do typical LUnix apps. need 2k?)
+}
+MEMORY {
+    ZP:  start = $0080, size = $0040;
+    RAM: start = %S,    size = $7600 - __STACKSIZE__;
+}
+SEGMENTS {
+    ZEROPAGE: load = ZP,  type = zp,  define = yes;                 # Pseudo-registers
+    STARTUP:  load = RAM, type = ro;                                # First initialization code
+    LOWCODE:  load = RAM, type = ro,                optional = yes; # Legacy from other platforms
+    INIT:     load = RAM, type = ro,  define = yes, optional = yes; # Library initialization code
+    CODE:     load = RAM, type = ro;                                # Program
+    RODATA:   load = RAM, type = ro;                                # Literals, constants
+    DATA:     load = RAM, type = rw;                                # Initialized variables
+    BSS:      load = RAM, type = bss, define = yes;                 # Uninitialized variables
+}
+FEATURES {
+    CONDES: type    = constructor,
+            label   = __CONSTRUCTOR_TABLE__,
+            count   = __CONSTRUCTOR_COUNT__,
+            segment = INIT;
+    CONDES: type    = destructor,
+            label   = __DESTRUCTOR_TABLE__,
+            count   = __DESTRUCTOR_COUNT__,
+            segment = RODATA;
+    CONDES: type    = interruptor,
+            label   = __INTERRUPTOR_TABLE__,
+            count   = __INTERRUPTOR_COUNT__,
+            segment = RODATA,
+            import  = __CALLIRQ__;
+}
+FILES {
+    %O: format = o65;
+}
+FORMATS {
+    o65: os     = lunix,
+         type   = small,
+         export = main,         # Program entry-point
+         import = LUNIXKERNEL;  # Kernel entry-points
+}