Improve configure tests for ffsl
Improve configure tests for ffsl

In particular:
- ffsl always returns int, not long, on FreeBSD, Linux, and OSX.
- Mute compiler warnings about rv being unused (and the potential for
   compilers optimizing out the call completely) by dumping the value
   with printf(3).

Signed-off-by: Garrett Cooper <94c72ae9cb99b268ef5bac9a1283c7f5ad375547@gmail.com>

TeamExodus/external_jemalloc,CMRemix/android_external_jemalloc,android-ia/platform_external_jemalloc,VRToxin/android_external_jemalloc,android-ia/platform_external_jemalloc,Snaipe/jemalloc,ahmetmircik/jemalloc,wqfish/jemalloc,vashstorm/jemalloc,cpeterso/jemalloc,yy-nm/jemalloc,flyfeifan/jemalloc,dxq-git/jemalloc,geekboxzone/lollipop_external_jemalloc,vashstorm/jemalloc,lvfeng1130/jemalloc,CyanogenMod/android_external_jemalloc,percona/jemalloc-debian,8l/jemalloc,VRToxin/android_external_jemalloc,wespelee/jemalloc,geekboxzone/mmallow_external_jemalloc,wespelee/jemalloc,garoose/jemalloc,8l/jemalloc,AndroidExternal/jemalloc,jemalloc/jemalloc-cmake,shekkbuilder/jemalloc,sudosurootdev/external_jemalloc,geekboxzone/mmallow_external_jemalloc,Snaipe/jemalloc,vashstorm/jemalloc,8l/jemalloc,CMRemix/android_external_jemalloc,ahmetmircik/jemalloc,sudosurootdev/external_jemalloc,tempbottle/jemalloc,shekkbuilder/jemalloc,leebaok/jemalloc-4.2.1-readcode,android-ia/platform_external_jemalloc,yy-nm/jemalloc,xin3liang/platform_external_jemalloc,kmiku7/jemalloc,yy-nm/jemalloc,CMRemix/android_external_jemalloc,wfxiang08/jemalloc,geekboxzone/lollipop_external_jemalloc,CyanogenMod/android_external_jemalloc,cpeterso/jemalloc,garoose/jemalloc,sudosurootdev/external_jemalloc,wqfish/jemalloc,wespelee/jemalloc,tempbottle/jemalloc,glandium/jemalloc,vashstorm/jemalloc,lilothar/jemalloc,AndroidExternal/jemalloc,jemalloc/jemalloc-cmake,glandium/jemalloc,AndroidExternal/jemalloc,lvfeng1130/jemalloc,sudosurootdev/external_jemalloc,glandium/jemalloc,geekboxzone/lollipop_external_jemalloc,Snaipe/jemalloc,kmiku7/jemalloc,awreece/jemalloc,android-ia/platform_external_jemalloc,flyfeifan/jemalloc,garoose/jemalloc,xin3liang/platform_external_jemalloc,leebaok/jemalloc-4.2.1-readcode,garoose/jemalloc,lilothar/jemalloc,lvfeng1130/jemalloc,lvfeng1130/jemalloc,Dmitry-Me/jemalloc,shekkbuilder/jemalloc,geekboxzone/mmallow_external_jemalloc,flyfeifan/jemalloc,kmiku7/jemalloc,geekboxzone/mmallow_external_jemalloc,awreece/jemalloc,glandium/jemalloc,wfxiang08/jemalloc,dxq-git/jemalloc,flyfeifan/jemalloc,leebaok/jemalloc-4.2.1-readcode,xin3liang/platform_external_jemalloc,geekboxzone/lollipop_external_jemalloc,percona/jemalloc-debian,xin3liang/platform_external_jemalloc,wqfish/jemalloc,Dmitry-Me/jemalloc,VRToxin/android_external_jemalloc,wespelee/jemalloc,kmiku7/jemalloc,Dmitry-Me/jemalloc,tempbottle/jemalloc,cpeterso/jemalloc,cpeterso/jemalloc,jemalloc/jemalloc-cmake,8l/jemalloc,dxq-git/jemalloc,leebaok/jemalloc-4.2.1-readcode,ahmetmircik/jemalloc,tempbottle/jemalloc,CyanogenMod/android_external_jemalloc,lilothar/jemalloc,VRToxin/android_external_jemalloc,percona/jemalloc-debian,wqfish/jemalloc,yy-nm/jemalloc,AndroidExternal/jemalloc,TeamExodus/external_jemalloc,CMRemix/android_external_jemalloc,TeamExodus/external_jemalloc,percona/jemalloc-debian,Dmitry-Me/jemalloc,wfxiang08/jemalloc,jemalloc/jemalloc-cmake,CyanogenMod/android_external_jemalloc,dxq-git/jemalloc,lilothar/jemalloc,TeamExodus/external_jemalloc,shekkbuilder/jemalloc,awreece/jemalloc,awreece/jemalloc,wqfish/jemalloc,Snaipe/jemalloc,wfxiang08/jemalloc,ahmetmircik/jemalloc