[regexp] move regexp parser into own files.

BUILD.gn

Index: BUILD.gn
diff --git a/BUILD.gn b/BUILD.gn
index ef0a55260013ddb45ecb21718f9e70a22ee43c5e..553e5d374c17f474aad2dfcd625fd2508870ce36 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -1185,6 +1185,8 @@ source_set("v8_base") {
     "src/regexp/jsregexp-inl.h",
     "src/regexp/jsregexp.cc",
     "src/regexp/jsregexp.h",
+    "src/regexp/regexp-ast.cc",
+    "src/regexp/regexp-ast.h",
     "src/regexp/regexp-macro-assembler-irregexp-inl.h",
     "src/regexp/regexp-macro-assembler-irregexp.cc",
     "src/regexp/regexp-macro-assembler-irregexp.h",
@@ -1192,6 +1194,8 @@ source_set("v8_base") {
     "src/regexp/regexp-macro-assembler-tracer.h",
     "src/regexp/regexp-macro-assembler.cc",
     "src/regexp/regexp-macro-assembler.h",
+    "src/regexp/regexp-parser.cc",
+    "src/regexp/regexp-parser.h",
     "src/regexp/regexp-stack.cc",
     "src/regexp/regexp-stack.h",
     "src/register-configuration.cc",