gcc-5.3.0: fix new build error with recent host gcc

newer gccs default to -std=c++17 which no longer allows
operator++ to be used on 'bool's.
this patch changes the type to unsigned char, just like
newer gcc versions have it.

patches/gcc-5.3.0/0024-gcc-reload-spill-bool.diff

@@ -0,0 +1,11 @@
+--- gcc-5.3.0/gcc/reload.h
++++ gcc-5.3.0.orig/gcc/reload.h
+@@ -168,7 +168,7 @@
+      value indicates the level of indirect addressing supported, e.g., two
+      means that (MEM (MEM (REG n))) is also valid if (REG n) does not get
+      a hard register.  */
+-  bool x_spill_indirect_levels;
++  unsigned char x_spill_indirect_levels;
+ 
+   /* True if caller-save has been reinitialized.  */
+   bool x_caller_save_initialized_p;