Misc. portability fixes.

src/platform-linux.cc

Index: src/platform-linux.cc
===================================================================
--- src/platform-linux.cc	(revision 1536)
+++ src/platform-linux.cc	(working copy)
@@ -42,8 +42,8 @@
 #include <sys/types.h>  // mmap & munmap
 #include <sys/mman.h>   // mmap & munmap
 #include <sys/stat.h>   // open
-#include <sys/fcntl.h>  // open
-#include <unistd.h>     // getpagesize
+#include <fcntl.h>      // open
+#include <unistd.h>     // sysconf
 #include <execinfo.h>   // backtrace, backtrace_symbols
 #include <strings.h>    // index
 #include <errno.h>
@@ -230,14 +230,14 @@
 
 
 size_t OS::AllocateAlignment() {
-  return getpagesize();
+  return sysconf(_SC_PAGESIZE);
 }
 
 
 void* OS::Allocate(const size_t requested,
                    size_t* allocated,
                    bool executable) {
-  const size_t msize = RoundUp(requested, getpagesize());
+  const size_t msize = RoundUp(requested, sysconf(_SC_PAGESIZE));
   int prot = PROT_READ | PROT_WRITE | (executable ? PROT_EXEC : 0);
   void* mbase = mmap(NULL, msize, prot, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
   if (mbase == MAP_FAILED) {