MFC r357903: ncurses: correct check for gcc >= 5.0

The hack in question is intended to workaround seemingly bogus #line markers
in cpp output. As far as I can tell, llvm cpp doesn't do this by default, so
there's no reason to add -P.

In our /bin/sh, the main incantation should be placed in a sub-shell in
order to properly pipe the output to fgrep.

The main motivation for this change is admittedly to stop emitting the noise
about clang not being gcc in make -s buildworld

Copy head@r302406 to stable/11 as part of the 11.0-RELEASE cycle.
Prune svn:mergeinfo from the new branch, as nothing has been merged
here.

Additional commits post-branch will follow.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Make ncurses build with GCC 5.0 and up

Merge the end result of two upstream changes:

Original fix from 20141206:
+ modify MKlib_gen.sh to work around change in development version of
gcc introduced here:
https://gcc.gnu.org/ml/gcc-patches/2014-06/msg02185.html
https://gcc.gnu.org/ml/gcc-patches/2014-07/msg00236.html
(reports by Marcus Shawcroft, Maohui Lei).

Later fixed in different manner in 20150725:
+ use alternate workaround for gcc 5.x feature (adapted from patch by
Mikhail Peselnik).

MFV r262639: ncurses 5.9 20140222 snapshot.

Requested by: bapt

MFV r262617: ncurses 5.9.

Merge r198489 from vendor/ncurses/dist:

Pull upstream patch to fix ee(1) crash when received SIGWINCH:

modify _nc_wgetch() to check for a -1 in the fifo, e.g., after a
SIGWINCH, and discard that value, to avoid confusing application
(patch by Eygene Ryabinkin, FreeBSD bin/136223).

PR: 136223
Submitted by: Eygene Ryabinkin
Obtained from: ncurses-5.7-20091024 snapshot
MFC after: 3 days

- Update ncurses to 5.7-20081102 (5.7 release) and build glue
- This also removes $FreeBSD$ from two now unmodifed source files
ncurses/tinfo/lib_raw.c and ncurses/tinfo/lib_baudrate.c

MFC after: 2 months (after 7.1 and 6.4 are released)

This commit was generated by cvs2svn to compensate for changes in r178866,
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This commit was generated by cvs2svn to compensate for changes in r174993,
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- Resolve conflicts
- Remove files that are removed in vender branch

Approved by: delphij

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