[libc++] Make parameter names consistent and enforce the naming style using readability-identifier-naming

Ensure that parameter names have the style `__lower_case`

Reviewed By: ldionne, #libc

Spies: aheejin, sstefan1, libcxx-commits, miyuki

Differential Revision: https://reviews.llvm.org/D129051

NOKEYCHECK=True
GitOrigin-RevId: b48c5010a46246cc3337244f7e2736dacf5889dc
diff --git a/include/regex b/include/regex
index bd04017..850fe09 100644
--- a/include/regex
+++ b/include/regex
@@ -1330,9 +1330,9 @@
 }
 
 inline _LIBCPP_INLINE_VISIBILITY
-bool __is_07(unsigned char c)
+bool __is_07(unsigned char __c)
 {
-    return (c & 0xF8u) ==
+    return (__c & 0xF8u) ==
 #if defined(__MVS__) && !defined(__NATIVE_ASCII_F)
         0xF0;
 #else
@@ -1341,9 +1341,9 @@
 }
 
 inline _LIBCPP_INLINE_VISIBILITY
-bool __is_89(unsigned char c)
+bool __is_89(unsigned char __c)
 {
-    return (c & 0xFEu) ==
+    return (__c & 0xFEu) ==
 #if defined(__MVS__) && !defined(__NATIVE_ASCII_F)
         0xF8;
 #else
@@ -1352,12 +1352,12 @@
 }
 
 inline _LIBCPP_INLINE_VISIBILITY
-unsigned char __to_lower(unsigned char c)
+unsigned char __to_lower(unsigned char __c)
 {
 #if defined(__MVS__) && !defined(__NATIVE_ASCII_F)
     return c & 0xBF;
 #else
-    return c | 0x20;
+    return __c | 0x20;
 #endif
 }
 
@@ -2057,9 +2057,9 @@
 
 template <class _CharT>
 _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
-bool __is_eol(_CharT c)
+bool __is_eol(_CharT __c)
 {
-    return c == '\r' || c == '\n';
+    return __c == '\r' || __c == '\n';
 }
 
 template <class _CharT>
@@ -2963,7 +2963,7 @@
         __parse_awk_escape(_ForwardIterator __first, _ForwardIterator __last,
                           basic_string<_CharT>* __str = nullptr);
 
-    bool __test_back_ref(_CharT c);
+    bool __test_back_ref(_CharT);
 
     _LIBCPP_INLINE_VISIBILITY
     void __push_l_anchor();
@@ -4782,9 +4782,9 @@
 
 template <class _CharT, class _Traits>
 bool
-basic_regex<_CharT, _Traits>::__test_back_ref(_CharT c)
+basic_regex<_CharT, _Traits>::__test_back_ref(_CharT __c)
 {
-    unsigned __val = __traits_.value(c, 10);
+    unsigned __val = __traits_.value(__c, 10);
     if (__val >= 1 && __val <= 9)
     {
         if (__val > mark_count())