Make PCRE's JIT work on Android devices

__clear_cache is missing from Android; use cacheflush instead.

Backport in Qt's own PCRE copy of the upstream fix:
http://vcs.pcre.org/viewvc?view=revision&revision=1340

Task-number: QTBUG-31754
Change-Id: I4996265f7b19343ba24983d4f8b2f75e2b578504
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

src/3rdparty/pcre/patches/README

@@ -0,0 +1,3 @@
+These patches are landed in upstream PCRE (they're marked with
+their SVN revision number). When upgrading PCRE remember check
+if the version you're upgrading to already contains them or not.

src/3rdparty/pcre/patches/r1340_fix_jit_on_android.patch

@@ -0,0 +1,18 @@
+Index: sljit/sljitConfigInternal.h
+===================================================================
+--- sljit/sljitConfigInternal.h	(revision 1339)
++++ sljit/sljitConfigInternal.h	(working copy)
+@@ -221,6 +221,13 @@
+ #define SLJIT_CACHE_FLUSH(from, to) \
+ 	sys_icache_invalidate((char*)(from), (char*)(to) - (char*)(from))
+ 
++#elif defined __ANDROID__
++
++/* Android lacks __clear_cache; instead, cacheflush should be used. */
++
++#define SLJIT_CACHE_FLUSH(from, to) \
++    cacheflush((long)(from), (long)(to), 0)
++
+ #elif (defined SLJIT_CONFIG_PPC_32 && SLJIT_CONFIG_PPC_32) || (defined SLJIT_CONFIG_PPC_64 && SLJIT_CONFIG_PPC_64)
+ 
+ /* The __clear_cache() implementation of GCC is a dummy function on PowerPC. */

src/3rdparty/pcre/sljit/sljitConfigInternal.h

@@ -217,6 +217,13 @@
 #define SLJIT_CACHE_FLUSH(from, to) \
 	sys_icache_invalidate((char*)(from), (char*)(to) - (char*)(from))
 
+#elif defined __ANDROID__
+
+/* Android lacks __clear_cache; instead, cacheflush should be used. */
+
+#define SLJIT_CACHE_FLUSH(from, to) \
+    cacheflush((long)(from), (long)(to), 0)
+
 #elif (defined SLJIT_CONFIG_PPC_32 && SLJIT_CONFIG_PPC_32) || (defined SLJIT_CONFIG_PPC_64 && SLJIT_CONFIG_PPC_64)
 
 /* The __clear_cache() implementation of GCC is a dummy function on PowerPC. */