lower default stack space to 512KB, update readme

README.md

@@ -124,8 +124,8 @@ Note, you can quit picoc's interactive mode using control-D.
 # Environment variables
 
 In some cases you may want to change the picoc stack space. The default stack
-size is 1MB (PICOC_STACK_SIZE in picoc.c) which should be large enough for most
-programs.
+size is 512KB (see PICOC_STACK_SIZE in picoc.c) which should be large enough
+for most programs.
 
 To change the stack size you can set the STACKSIZE environment variable to a
 different value. The value is in bytes.

picoc.c

@@ -12,7 +12,8 @@
 #include <string.h>
 
 /* Override via STACKSIZE environment variable */
-#define PICOC_STACK_SIZE (1024*1024)              /* space for the the stack */
+/* stack space */
+#define PICOC_STACK_SIZE (512000)
 
 int main(int argc, char **argv)
 {