This commit attempts to fix the following error:
intern\guardedalloc\intern\mallocn.c: In function 'rem_memblock':
intern\guardedalloc\intern\mallocn.c:977:48: error: conversion to 'intptr_t' from 'size_t' may change the sign of the result [-Werror=sign-conversion]
From the references I've managed to find, it appears that
the second arg to munmap() should be size_t not intptr_t.
Fortunately though, we don't use this arg anyways atm, so
this should be quite harmless...
