Remove a bogus workaround for old GCC

At least starting with ca83115b
the source code cannot be compiled with anything older than GCC 4.8.5.

Furthermore, 64-bit atomic read-modify-write operations on IA-32
would depend on the LOCK CMPXCHG8B instruction, which was introduced
in the Intel Pentium. Our IA-32 builds ought to be -march=i686
starting with commit 9cabc9fd.

Approved by Sergei Golubchik

configure.cmake

@@ -60,15 +60,6 @@ IF(CMAKE_CXX_COMPILER_ID MATCHES "GNU|Clang" AND (NOT MSVC))
   ENDIF()
 ENDIF()
 
-# workaround for old gcc on x86, gcc atomic ops only work under -march=i686
-IF(CMAKE_SYSTEM_PROCESSOR STREQUAL "i686" AND CMAKE_COMPILER_IS_GNUCC AND
-   CMAKE_C_COMPILER_VERSION VERSION_LESS "4.4.0")
-  SET(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -march=i686")
-  SET(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -march=i686")
-  # query_response_time.cc causes "error: unable to find a register to spill"
-  SET(PLUGIN_QUERY_RESPONSE_TIME NO CACHE BOOL "Disabled, gcc is too old")
-ENDIF()
-
 # use runtime atomic-support detection in aarch64
 IF(CMAKE_SYSTEM_PROCESSOR MATCHES "aarch64")
   MY_CHECK_AND_SET_COMPILER_FLAG("-moutline-atomics")