InstallBuiltinFunctionIds stood out when looking at code that grew
strangely when compiled with default optimizations.

This change from repeated code to a loop saves 6-7 KB of machine code.
I suspect it's faster but I also suspect it's fast enough either way so
that is not really a factor. Machine code reduction seen below.

Code formatted with git cl format.

clang x64:
Total change: -5985 bytes
-------------------------------------------
 +517 - Source: ?? - (gained 744, lost 227)
-------------------------------------------
  New symbols:
       +744: v8::internal::Genesis::InstallBuiltinFunctionIds()::builtins type=d, size=744 bytes
  Removed symbols:
         -4: .L.str98 type=r, size=4 bytes
... [stripped 30 similar lines]
        -19: .L.str100 type=r, size=19 bytes

----------------------------------------------------------------------------------------------
 -6502 - Source: /home/bratell/src/chromium/src/v8/src/bootstrapper.cc - (gained 0, lost 6502)
----------------------------------------------------------------------------------------------
  Removed symbols:
      -1135: v8::internal::ResolveBuiltinIdHolder(v8::internal::Handle<v8::internal::Context>, char const*) type=t, size=1135 bytes
  Shrunk symbols:
      -5367: v8::internal::Genesis::InstallBuiltinFunctionIds() type=t, (was 7105 bytes, now 1738 bytes)

BUG=

Review URL: https://codereview.chromium.org/918303005

Cr-Commit-Position: refs/heads/master@{#26919}