Add a --with-oprofile flag to configure, which uses OProfile's agent

Add a --with-oprofile flag to configure, which uses OProfile's agent
library to tell it the addresses of JITted functions.  For a
particular program, this changes the opreport -l output from:

samples %    image name        symbol name
48182  98.9729 anon (tgid:19412 range:0x7f12ccaab000-0x7f12cdaab000) anon (tgid:19412 range:0x7f12ccaab000-0x7f12cdaab000)
11     0.0226  libstdc++.so.6.0.9    /usr/lib/libstdc++.so.6.0.9

to:

samples %    image name        symbol name
24565  60.7308 19814.jo        fib_left
15365  37.9861 19814.jo        fib_right
22     0.0544  ld-2.7.so       do_lookup_x

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@75279 91177308-0d34-0410-b5e6-96231b3b80d8