Move modulemap to header search directory. NFC intended.

In code we use `#include "swift/Lib/Header.h"` which is located in
"include/swift/Lib/Header.h", so we use "include/" as a header search
path. We should put modulemaps in the same directory and shouldn't rely
on clang to search in immediate subdirectories.

rdar://106677321

include/module.modulemap

@@ -0,0 +1,48 @@
+module BasicBridging {
+  header "swift/Basic/BridgedSwiftObject.h"
+  header "swift/Basic/BasicBridging.h"
+  header "swift/Basic/SourceLoc.h"
+  requires cplusplus
+  export *
+}
+
+module CBasicBridging {
+  header "swift/Basic/CBasicBridging.h"
+}
+
+module ASTBridging {
+  header "swift/AST/AnyFunctionRef.h"
+  header "swift/AST/ASTBridging.h"
+  header "swift/AST/Builtins.h"
+  header "swift/AST/DiagnosticEngine.h"
+  header "swift/AST/DiagnosticConsumer.h"
+  header "swift/AST/ForeignAsyncConvention.h"
+  header "swift/AST/ForeignErrorConvention.h"
+  header "swift/AST/SubstitutionMap.h"
+
+  textual header "swift/AST/Builtins.def"
+
+  requires cplusplus
+  export *
+}
+
+module CASTBridging {
+  header "swift/AST/CASTBridging.h"
+}
+
+module SILBridging {
+  header "swift/SIL/SILBridging.h"
+  header "swift/SIL/SILLocation.h"
+  requires cplusplus
+  export *
+}
+
+module OptimizerBridging {
+  header "swift/SILOptimizer/OptimizerBridging.h"
+  export *
+}
+
+module _RegexParserBridging {
+  header "swift/Parse/RegexParserBridging.h"
+  export *
+}

include/swift/module.modulemap

@@ -1,48 +0,0 @@
-module BasicBridging {
-  header "Basic/BridgedSwiftObject.h"
-  header "Basic/BasicBridging.h"
-  header "Basic/SourceLoc.h"
-  requires cplusplus
-  export *
-}
-
-module CBasicBridging {
-  header "Basic/CBasicBridging.h"
-}
-
-module ASTBridging {
-  header "AST/AnyFunctionRef.h"
-  header "AST/ASTBridging.h"
-  header "AST/Builtins.h"
-  header "AST/DiagnosticEngine.h"
-  header "AST/DiagnosticConsumer.h"
-  header "AST/ForeignAsyncConvention.h"
-  header "AST/ForeignErrorConvention.h"
-  header "AST/SubstitutionMap.h"
-
-  textual header "AST/Builtins.def"
-
-  requires cplusplus
-  export *
-}
-
-module CASTBridging {
-  header "AST/CASTBridging.h"
-}
-
-module SILBridging {
-  header "SIL/SILBridging.h"
-  header "SIL/SILLocation.h"
-  requires cplusplus
-  export *
-}
-
-module OptimizerBridging {
-  header "SILOptimizer/OptimizerBridging.h"
-  export *
-}
-
-module _RegexParserBridging {
-  header "Parse/RegexParserBridging.h"
-  export *
-}