Add Chromium-only Blender WebEngine parity work

blender-5.2.0/extern/gmp-source/mpn/generic/scan0.c

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+/* mpn_scan0 -- Scan from a given bit position for the next clear bit.
+
+Copyright 1994, 1996, 2001, 2002, 2004 Free Software Foundation, Inc.
+
+This file is part of the GNU MP Library.
+
+The GNU MP Library is free software; you can redistribute it and/or modify
+it under the terms of either:
+
+  * the GNU Lesser General Public License as published by the Free
+    Software Foundation; either version 3 of the License, or (at your
+    option) any later version.
+
+or
+
+  * the GNU General Public License as published by the Free Software
+    Foundation; either version 2 of the License, or (at your option) any
+    later version.
+
+or both in parallel, as here.
+
+The GNU MP Library is distributed in the hope that it will be useful, but
+WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+for more details.
+
+You should have received copies of the GNU General Public License and the
+GNU Lesser General Public License along with the GNU MP Library.  If not,
+see https://www.gnu.org/licenses/.  */
+
+#include "gmp-impl.h"
+#include "longlong.h"
+
+/* Argument constraints:
+   1. U must sooner or later have a limb with a clear bit.
+ */
+
+mp_bitcnt_t
+mpn_scan0 (mp_srcptr up, mp_bitcnt_t starting_bit)
+{
+  mp_size_t starting_word;
+  mp_limb_t alimb;
+  int cnt;
+  mp_srcptr p;
+
+  /* Start at the word implied by STARTING_BIT.  */
+  starting_word = starting_bit / GMP_NUMB_BITS;
+  p = up + starting_word;
+  alimb = *p++ ^ GMP_NUMB_MASK;
+
+  /* Mask off any bits before STARTING_BIT in the first limb.  */
+  alimb &= - (mp_limb_t) 1 << (starting_bit % GMP_NUMB_BITS);
+
+  while (alimb == 0)
+    alimb = *p++ ^ GMP_NUMB_MASK;
+
+  count_trailing_zeros (cnt, alimb);
+  return (p - up - 1) * GMP_NUMB_BITS + cnt;
+}