Fix build failure on NetBSD/arm 6.1.  PR/47941
 - fix configure scripts to detect !G_ATOMIC_LOCK_FREE correctly
   (use AC_TRY_LINK rather than AC_TRY_COMPILE to see if symbols are defined)
 - fix prototype mismatches in !G_ATOMIC_LOCK_FREE case
   (note no binary changes in G_ATOMIC_LOCK_FREE case)

"please commit it" from agc@.
Add workaround for PR/47798 (png gets SEGV on NetBSD/arm 6.1 due to gcc bug).
 - specify "-O2 -fno-ipa-sra" for NetBSD/arm and gcc-4.5.* in hacks.mk
 - also bump PKGREVISION for explicit rebuild

"Please commit that" from wiz@.
Updated graphics/png to 1.6.2nb1
Fixing the clang build by breaking the gcc build is not on. Hi, Joerg.
preprocessor is a tool.
Pull more post-3.2.0 fixes from upstream (leaf package bug fixes):
http://mlterm.sf.net/mlterm-3.2.0-fixes.patch
 - Fix the bug which caused segmentation fault in closing input method
   status window.
 - Fix the error message in the failure of loading US-ASCII font.
 - Resize the window in attaching a new pty. (enbugged at 3.2.0)
 - Fix the bug which lets parcellite reset the selected region.
 - Fix the bug which disabled mlconfig and mlterm-menu. (enbugged at 3.2.0)
 - SF Bug #3614192

Bump PKGREVISION.
Updated x11/mlterm to 3.2.0nb5