Merge branch 'da/rhel7-lacks-uncompress2-and-c99'

Adjust build on RHEL 7 to explicitly ask C99 support and use
the fallback implementation of uncompress2 we ship.

* da/rhel7-lacks-uncompress2-and-c99:
  build: centos/RHEL 7 ships with an older gcc and zlib

diff --combined config.mak.uname
index 9b3e9bff5f5f8be12483a4b6001921b399373357,5ed1d8755fd07dea221e5c3a8c564f0b34c49e9b..c48db45106c8dc0e4138ccb8ecff016f3f7d0faa
--- 1/config.mak.uname
--- 2/config.mak.uname
+++ b/config.mak.uname
@@@ -63,6 -63,11 +63,11 @@@ ifeq ($(uname_S),Linux
        PROCFS_EXECUTABLE_PATH = /proc/self/exe
        HAVE_PLATFORM_PROCINFO = YesPlease
        COMPAT_OBJS += compat/linux/procinfo.o
+       # centos7/rhel7 provides gcc 4.8.5 and zlib 1.2.7.
+       ifneq ($(findstring .el7.,$(uname_R)),)
+               BASIC_CFLAGS += -std=c99
+               NO_UNCOMPRESS2 = YesPlease
+       endif
  endif
  ifeq ($(uname_S),GNU/kFreeBSD)
        HAVE_ALLOCA_H = YesPlease
@@@ -576,7 -581,6 +581,7 @@@ ifeq ($(uname_S),NONSTOP_KERNEL
        NO_SETENV = YesPlease
        NO_UNSETENV = YesPlease
        NO_MKDTEMP = YesPlease
 +      NO_UNCOMPRESS2 = YesPlease
        # Currently libiconv-1.9.1.
        OLD_ICONV = UnfortunatelyYes
        NO_REGEX = NeedsStartEnd