Improve the diagnostics of the number-reading preprocessor directives.

The GNU line marker directive was sharing code with the #line directive, but some of the warnings/errors were reporting as #line directive diagnostics in both cases.

Previously:
#line 11foo1   ==> "#line directive requires a simple digit sequence"
# 11foo1       ==> "#line directive requires a simple digit sequence"

Now, we get:
#line 11foo1   ==> "#line directive requires a simple digit sequence"
# 11foo1       ==> "GNU line marker directive requires a simple digit sequence"




git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@179139 91177308-0d34-0410-b5e6-96231b3b80d8
Repeat some #line directive tests for the GNU line marker directive.



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@179142 91177308-0d34-0410-b5e6-96231b3b80d8
[frontend] -frewrite-includes: if there was no inclusion, don't add lineinfo that indicates return from another file.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@179143 91177308-0d34-0410-b5e6-96231b3b80d8
[frontend] When preprocessing, turn implicit module imports into @imports.

part of rdar://13610250

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@179144 91177308-0d34-0410-b5e6-96231b3b80d8
[frontend] -frewrite-includes: turn implicit module imports into @imports.

rdar://13610250

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@179145 91177308-0d34-0410-b5e6-96231b3b80d8